Abu Dhabi Part 1
Abu Dhabi Part 1
Abu Dhabi Part 1
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ROADWAY DESIGN MANUAL Roads and Bridges
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ROADWAY DESIGN MANUAL Roads and Bridges
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ROADWAY DESIGN MANUAL Roads and Bridges
The Manual is intended to serve as a guide for the Revisions and additions to this manual will be
design of the roads and highways that fall under issued from time to time as required. This section
the jurisdiction of the Road Section, Abu Dhabi contains information regarding technical
Municipality. The Manual provides a range of memorandums used to submit future revisions
acceptable values for critical dimensions and and additions.
outlines parameters that will help designers
conform to the expectations of the Road Section Further contained in this section is an overview of
of the Abu Dhabi Municipality. It is assumed the layout of the manual content, roadway
that the user has the educational and engineering classifications, route designations connecting
experience necessary to properly implement its U.A.E cities and emirates, and streets and place
procedures, guidelines and criteria. names as assigned by Abu Dhabi Municipality.
It is perceived that this manual will promote the 102 CONTENTS AND
following: ORGANIZATION
1. All designs will be based on identical The scope of the Roadway Design Manual is
criteria. comprehensive, and is divided into three parts.
2. Plans will have a consistent, The three parts are further divided into sections,
well-organized format which will not each with appropriate sub-sections. The three
vary greatly from project to project. parts are:
3. Familiarization of criteria and procedures
will be simplified. Part 1 Roadway Development
4. The technical review process will be Part 2 Roadway Design
expedited for both the Road Section and Part 3 Structures and Bridges
the Consultant.
5. Cost efficiencies will be realized during 102.01 PART 1: ROADWAY
design by an early understanding of DEVELOPMENT
procedures and criteria to be employed.
The purpose of the Roadway Development part is
The manual is presented in loose-leaf form to to outline the information and data which must be
facilitate revisions and additions. This manual analyzed to determine a projects scope. This
utilized established analysis techniques and design information and analyses are assembled into a
standards from recognized technical associations Design Concept Report, which becomes the basis
that are listed as references in Appendix A. for the project design.
When the Roadway Design Manual is combined The Roadway Development part is divided into
with the four companion documents listed below, three sections. The first section explains the
the standardization of the planning, design and formal organization of this manual and the other
construction of roadway projects will be two sections, the Design Concept Development
Part 1 100-1
ROADWAY DESIGN MANUAL Roads and Bridges
and the Design Concept Reports, define the Roadway Design part, this document is intended
conceptual design of the project. to be used in conjunction with the Standard
Specifications and the Abu Dhabi Standard
The Design Concept Section includes subsections Drawings for the standardization of details for
in Transportation Planning, Socio-economic structures and bridges.
Data, and Technical Investigations. Conceptual
Design must be based upon site specific Uniform design and construction of structures and
community considerations that reflect military, bridges promotes efficiency of design,
utility, environmental features, physical properties construction, and maintenance. This part focuses
of the site, and circulation that define the project on features incorporating sound design and cost-
design. To support the lands intended use, effective design practices to meet this goal.
procurement of the information from departments
within the Municipality and outside of This part consists of nine sections that cover the
Municipalitys organization is required. general aspects of structures and bridge design.
Subjects covered include, General Design
All the Project-specific data collected forms the Criteria, Design Loads, Reinforced Concrete,
basis for the Design Concept Report, a summary Prestressed Concrete, Structural Steel,
of the technical analyses and schematic design Expansions and Contractions, Geotech and
that are to be used for plan preparation and Retaining Walls. The last section addresses
construction. miscellaneous items such as Traffic Supports,
Utilities and the Falsework Policy and
102.02 PART 2: ROADWAY DESIGN Requirements.
Part 1 100-2
ROADWAY DESIGN MANUAL Roads and Bridges
103.03 TECHNICAL MEMORANDUMS The design classes discussed in this section are
- SPECIFIC applicable to all highway networks in both rural
and urban areas under the jurisdiction of the Road
Technical Memorandums - Specific, deal with Section, Abu Dhabi Municipality.
issues or information that is of specific interest to
a particular section (design contract), and as such Table 100.01 summarizes the major
have no influence or effect on other design characteristics of the first tier classifications, i.e.,
sections. primary, secondary and local roads.
104.02 DESIGN
! Primary Roads
Freeways
Expressways
! Secondary Roads
Arterials
Collectors
! Local Roads
Part 1 100-3
ROADWAY DESIGN MANUAL Roads and Bridges
Table 100.01
Summary of Functional Characteristics for Roadway Classifications*
Part 1 100-4
ROADWAY DESIGN MANUAL Roads and Bridges
Table 100.02
Roadway Types by Functional Classification
Arterial Collector
Secondary (Main Roads) Major
Frontage Roads Minor
Part 1 100-5
ROADWAY DESIGN MANUAL Roads and Bridges
Table 100.03
Characteristics of Urban/Rural Design Classes
Freeways/ Arterials Collectors Locals
Expressways
Traffic Service:
Urban and Optimum mobility Traffic movement Traffic movement Traffic movement
Rural primary and land access of secondary
consideration equal importance. consideration
Land Service:
Urban and Full control of access Land access Traffic movement Land access
Rural no direct land access secondary in and land access of primary
consideration equal importance. consideration
Traffic Flow Characteristics:
Urban and Free flow Uninterrupted Interrupted flow Interrupted flow
Rural except at
intersections
Private and Commercial Access:
Urban and Not permitted None or limited Permitted Permitted
Rural
Connection Type for Public Roads:
Urban Grade separations & At-grade At-grade At-grade
interchanges intersections, intersections intersections
interchanges,
orslip-ramps
Rural Grade separations & At-grade At-grade At-grade
interchanges intersections or intersections intersections
interchanges
Connects to:
Urban Arterials Arterials Locals Arterials Locals
Expressways Expressways
Freeways
Rural Expressways Locals Collectors Locals Collectors Locals Collectors
Collectors Expressways
Freeways
Vehicle Type:
Urban All types up to 20 All types up to 20 All types Passenger &
percent heavy trucks percent heavy service vehicles
trucks
Rural All types; heavy trucks All types up to All types, up to Predominantly
average 20%-40% 40% trucks 30% heavy trucks passenger cars &
in the 3 mg to 5 light to medium
mg class trucks: occasional
heavy trucks
ADT (20):
Urban Level of Service is C/D 5,000-30,000 1,000-12,000 100-1,000
Rural Level of Service is C/D 2,000-15,000 200-4,000 0 to 300
Average Running Speed for Off-Peak Conditions:
Urban 80-110 kph 50-80 kph 30-50 kph 30-40 kph
Rural 80-120 kph 60-110 kph 50-90 kph 45-80 kph
Part 1 100-6
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 100.01
Route Designations Between U.A.E. Cities and Emirates
Part 1 100-7
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 100.02
Connections Between Primary and Secondary or Local Roads
Part 1 100-8
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-1
ROADWAY DESIGN MANUAL Roads and Bridges
The Consultant is responsible for providing base Coordinate Grid - Coordinate grid ticks shall be
mapping for design concept development. shown on the maps at intervals to suit drawing.
Specific requirements will be identified in the
Consultants scope of work. Existing aerial and North Arrow - A north arrow shall be placed on
topographic maps may be available and suitable each map sheet. The north arrow shall be
for use in consultation with the Department. The oriented so that north points to the top or to the
Abu Dhabi Municipality and Town Planning right of the map sheet. Match lines shall also be
Department maintain a limited library of existing labeled so that each sheet may be joined
mapping which the Consultant shall review for accurately to adjacent sheets.
background information.
Map Index - A sheet index diagram shall be
Mapping scales and contour intervals generally prepared for each mapping project. This diagram
suitable for the intended purpose are shown in shall show the position and relationship of each
Table 200.01. sheet to adjacent sheets. A title block is also
required and shall be placed on each sheet.
201.04.02 Topographic Mapping
Part 1 200-2
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.01
Standard Mapping Symbols - Boundaries and Monuments
Part 1 200-3
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.02
Standard Mapping Symbols - Natural Planimetric Features
Part 1 200-4
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.03
Standard Mapping Symbols - Manmade Planimetric Symbols
Part 1 200-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-6
ROADWAY DESIGN MANUAL Roads and Bridges
202.02.02 Growth Projections The development of all road and bridge projects
typically affects many public services. This can
The Abu Dhabi Municipalitys roadways are result from encroachment of the improvement
designed to serve the traffic volume anticipated project beyond the existing roadway, sidewalk,
during the next 20 years. Presently, historical and bridge. As such, pre-design coordination
records of past growth trends do not exist. with public services is required to incorporate
Therefore, it is important that a reasonable design approaches and construction phasing that
growth projection is used to size the project. minimize the project impact.
The growth can be categorized as an increase, The Consultant is responsible for identifying all
decrease or no change. It is anticipated that an public services which may be affected by the
increase will be the most probable scenario in the roadway/bridge project. In addition, the
foreseeable future. The rate of growth can be Consultant is also responsible to compile all
expected to increase linearly each year or relevant design requirements from the affected
exponentially (i.e., an order of growth magnitude public services and incorporate these parameters
each year). into the project design. It is the Consultants
responsibility to assure the Abu Dhabi
The growth projection can dramatically affect Municipality that the design and construction
project sizing. Therefore, the Consultant is phasing meets the approval of the affected public
expected to develop a realistic growth projection service.
which takes into consideration variables such as:
Table 200.03 identifies the various Public
increases in vehicle ownership Services and the responsible agency/authority for
land use each.
population growth rate, i.e. linear or
exponential Table 200.03
Public Services
In urban areas, growth projections are dependent Service Agency/Authority
upon the rate at which the Town Planning Master Road/Bridge
Plan is implemented, as well as the proposed Construction ADM-Road Section
types of land use. The Consultant is expected to Agriculture/Parks ADM-Agriculture
confer with the Town Planning Department to Police Police Directorate/
ascertain the rate at which the Town Planning Traffic Police Dept.
Master Plan is to be implemented. Fire Civil Defense Dept.
Security Defense Dept./CID
In the rural areas, information regarding growth is Schools Town Planning/
less defined. In these cases, it is necessary that Ministry of Education
the Consultant make growth projections. These Sanitation ADM - Health Section
projections should take into account any data Parking ADM - Road Section
concerning growth, including changes in land use Recreational Town Planning/
adjacent to the roadway. As a starting point, it Agriculture
can be assumed that the use of land is primarily Navigable Waters Coast Guard
agricultural, with an average growth of 1% to 2% Mail Service Postal Directorate
per year for a period of 20 years. Public Transportation ADM - Public Transport
Section
The resulting growth projection, along with
supporting data and the rationale used to 202.02.04 Schools
substantiate the project, shall be approved by the
Town Planning Section. Schools are an important national resource. The
design shall accommodate and preserve sufficient
202.02.03 Public Services access to all facilities that are affected by project
design. Therefore, the Consultant is expected to
Part 1 200-7
ROADWAY DESIGN MANUAL Roads and Bridges
adapt the projects design to accommodate each establishment and approval of all Service
schools needs. Reservations.
For each school, there are a number of factors Table 200.04 lists the Responsible
that must be considered in the project design. Agencies/Authorities for Utilities. A survey of
These include: existing utilities is required. The purpose of the
school bus traffic utilities survey is to determine which utilities can:
crosswalks remain in place based on field surveys, as-
school yard fencing built plans and other available information:
parking be protected and/or relocated; and,
landscaping affect the horizontal and vertical alignment of
noise attenuation (i.e., insulated windows, the roadway.
soundwalls)
other safety improvement In the case of future or relocated utilities, it may
relocation of affected structures, as necessary be necessary to preserve adjacent land for utility
affects on potential school expansion installation and relocation. The associated costs
for utility work shall be identified as part of the
In the case of new school site development, the design reflected in the project cost estimate for the
Town Planning Master Plan and Town Planning Design Concept Report. Refer to Part 1, Section
staff shall be consulted to identify these sites 321, Cost Estimate.
within and/or adjacent to the project limits.
Table 200.04
As with all other adjacent property improvements, Responsible Agency/Authority for Utilities
the Consultant is required to provide plans which Service Agency/ Authority
can be used to construct the necessary Water ADM-WED Water (Water and
improvements either in conjunction with the Electricity Dept.)
roadway/bridge project or as a separate project. Sewer ADM-Sanitary Drainage
This is intended so that construction can be Network Section
undertaken on the school sites during scheduled Telephone ETISILAT
school closures. Electricity ADM-WED Electrical (Water
and
202.02.05 Mosques Electricity Department.)
Lighting ADM-WED (Water and
Mosques are extremely important to the Islamic Electricity Department)
faith and cannot be relocated or impacted in any
way. The Consultant shall identify all Mosques 202.02.07 Security
within close proximity to a proposed project. The
project design shall avoid impact to Mosques and Nearly every project is affected by some level of
shall accommodate and preserve sufficient access security issue. All embassies, government
to these sites. installations, palaces, schools, banks and VIP
homes are protected by guards with guardhouses,
202.02.06 Utilities and associated channeling devices. As a result,
many of these facilities interfere with road and
Major road and bridge projects typically include bridge projects.
improvements to all affected utility services. This
also includes preparing plans and specifications The Consultant is required to minimize the
for these improvements. Pre-design activities relocation of affected facilities as part of the road
require coordination with many and bridge project. As with all other adjacent
agencies/departments. Final design approval of property improvements, the Consultant is required
the utility improvements by the utility agencies is to provide plans which can be used to construct
also required. The Utilities Section of the Town the necessary improvements either in conjunction
Planning Department is responsible for
Part 1 200-8
ROADWAY DESIGN MANUAL Roads and Bridges
The effects of commercial activities on the road calculation and survey to establish
and bridge design shall be taken into account. existing parking demand
For example, existing access shall be maintained future growth of parking demand, as a
as well as accommodating special features of the function of land development intensity,
non-project site. As a result, coordination with vehicle ownership/occupancy trends, etc.
the Town Planning Department, adjacent opportunity for mixed parking utilization
landowners and governmental departments is
required to lessen the impact of the road/bridge Both peak and off-peak parking demands should
improvement project on commercial activities. be included in the analysis.
Part 1 200-9
ROADWAY DESIGN MANUAL Roads and Bridges
Table 200.05
Existing and Future Parking Generation Rates (CBD)
Use Period Rate Vehicle Occupancy Vehicle Ownership
Factors Factors
Residential Existing 1 space/1000 SF .80 .67
Future 1 space/1000 SF .85 .80
Commercial Existing 1 space/500 SF .85 1.00
Future 1 space/500 SF .90 1.00
Part 1 200-10
ROADWAY DESIGN MANUAL Roads and Bridges
The Agriculture Section will assume The Consultant shall assess a proposed projects
responsibility for plantings and other special affect on ambient noise levels to determine
features. whether or not it will result in a significant
deterioration from the existing condition. Noise
Maintenance and operation of the irrigation sensitive receptors, such as Mosques, schools and
systems are the responsibility of the Agricultural residential dwellings, shall be identified within the
Section. project limits. The Consultant shall strive to
develop a design that will have the least increase
202.03.02 Topography in noise levels to these receptors.
Part 1 200-11
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-12
ROADWAY DESIGN MANUAL Roads and Bridges
goal of the Abu Dhabi Municipality to establish a next 20 years will increase exponentially.
permanent automated traffic data collection Formula B shall be used when the Engineer
system for the Municipality. However, until this judges that the traffic volume will increase
system is fully developed and implemented, the linearly.
specific procedures outlined in this section shall
be followed in the collection of traffic data for Formula A:
roadway and bridge projects. ADT (20) = ADT Present Growth Factor (GF)
20
The procedures which follow establish the Where GF = 1 + Annual % Traffic Growth
minimum requirements; however, this does not 100
preclude the Engineer from using more
sophisticated procedures if available. Formula B:
ADT (20) = ADT present +
203.03.02 Traffic Projections Annual % Traffic Growth ADT Present 20
100
The Abu Dhabi Municipalitys roadways are
designed to serve the traffic volume anticipated Examples:
during the next 20 years. Therefore, the existing The following is an example of the use of the two
Average Daily Traffic (ADT) must be projected formulas when the annual percent of traffic
over a 20-year time frame. For the 20-year travel growth is anticipated to be 10 percent and the
forecast, variables such as an increase in auto ADT at present is 4,000.
ownership and vehicle registration, population,
employment, and residential/ commercial/ Formula A:
industrial land uses which strongly influence the ADT (20) = 4,000 1 + 10 20
for the estimated traffic growth anticipated for the 100 100
next 20 years by considering all previously
acquired data regarding all activity growth in the = 4,000 [(1.15) 5 + (1.10)15]
proximity of the highway improvement. = 4,000 [(2.01) + (4.18)]
= 24,760
The following formulas may be applied under
assumptions of increasing, decreasing, or equal
percentages of traffic growth over the 20-year
projection. Formula A shall be used when the
Engineer judges that the traffic volume over the
Part 1 200-13
ROADWAY DESIGN MANUAL Roads and Bridges
Table 200.06 specifies the minimum procedures The need for setting new horizontal control points
that shall be met when traffic studies are will be ascertained from the existing data. A
conducted to identify the present ADT. discussion of surveying methods and procedures
Collection of traffic volumes for three functional used to establish new horizontal control points is
classes of highways (Primary, Secondary, and beyond the scope of this manual and will be
Local) and five types of improvements (up- covered in a companion Technical Manual on the
grading existing Primary or Secondary Roads; subject of surveying and mapping.
new Primary or Secondary Road on new
alignment/location; upgrading existing 203.04.03 Vertical Control
intersection/interchange on Primary or Secondary
Roads; new intersection/interchange on existing There are several vertical datum currently being
Primary or Secondary Roads; and new Local used for construction in Abu Dhabi. Table
Streets are considered. 200.07 summarizes the most common vertical
datum and the relationship between them. In
203.04 SURVEY CONTROL/FIELD addition, some Sewerage Projects Committee
SURVEYS projects use their own datum, in which + 100.00
meters equals 0.00 meters, New Abu Dhabi
203.04.01 Introduction Datum. All design work will be referred to the
New Abu Dhabi Datum.
Each project requires initial field surveys to
establish baseline topographic information for 203.04.04 Coordinate System
project scoping and design. Setting horizontal
and vertical control is of great importance in A Coordinate System has been established by
mapping. Relative position in the horizontal Abu Dhabi Municipality Town Planning
plane is maintained by horizontal control. Department. This Coordinate System shall be
Horizontal control consists of a series of points used for all surveys.
accurately fixed in position by distance and
direction in the horizontal plane. 203.04.05 Field Surveys
For most topographic surveying, traverses furnish Field Surveys will be required on nearly every
satisfactory control. For strip maps, the open project to supplement the aerial topography,
traverse is used. The open traverse can be tied to record underground utility or drainage features,
fixed points at each end. For area maps, the reflect new existing features, provide cross-
closed traverse is used. The closed traverse can sections and existing pavement elevations at the
be closed to form a net which is accurate to the limits of improvement, obtain building floor
degree required. elevations and other related information needed
for preliminary and final design.
Relative position in the vertical plane can be
maintained by a series of benchmarks in the map Once the horizontal alignment, including
area. These benchmarks are referred to a known applicable alternative alignments, has been
datum, usually mean sea level. established, the roadway centerline will be staked
Part 1 200-14
ROADWAY DESIGN MANUAL Roads and Bridges
in the field to enable close examination of the In absence of drainage master plans or other
roadway location by Department representatives pertinent studies to establish area hydrology, the
and Consultants staff. The staking interval and Consultant is responsible to develop/collect
definition of the project geometrics required will hydrologic data. This data is to include:
be determined on a project specific basis in
consultation with the Municipality rainfall measurement (volume and time) at a
Representative. suitable collection site, such as the airport
measurement of area run-off
A detailed survey of the existing greenery miscellaneous basic data such as soil type,
impacted by the project will be required. The land use, aerial photographs, infiltration,
survey will record the location, size and limits of evaporation, solar radiation and
all trees shrubs and flower beds within the limits oceanography
of improvement. Photographs should be taken to
supplement the data. This information will be Note that sources for miscellaneous data are
recorded on drawings and used to investigate scattered. The Consultant must rely upon the
alignment adjustments or alternatives that will collective experience of design in other similar
minimize the removal of greenery. areas to compile this information.
pump stations
outfalls
reinforced concrete box structures
channels
ditches
large diameter pipes
pumps, etc.
Part 1 200-15
ROADWAY DESIGN MANUAL Roads and Bridges
Table 200.06
Procedures for Traffic Studies
EXISTING ROADS
Primary or 24-hour counts for 7 continuous days for each of four yearly periods:
Secondary Roads March, April, May
June, July, August
September, October, November
December, January, February
24-hour manual traffic counts for trucks classified by axle for any three days from the following four days:
Sunday
Monday
Tuesday
Wednesday
Intersections Afternoon (or morning) and evening intersection peak hour counts summarized in 15-minute increments by direction (left turn, right turn
and through movements). Counts taken on Sunday or Wednesday, Monday and Tuesday. Hourly summary of same includes separate totals
for:
Passenger vehicles, vans, pick-up trucks
Buses
Trucks by axle count
Local Streets 12-hour manual counts taken from 6 a.m. to 6 p.m. on Sunday, (or Wednesday), Monday and Tuesday. Total hourly volumes shall be
recorded.
Convert to 24-hour ADT by multiplying the 12-hour volume by 2. This will provide a conservative estimate of the 24-hour ADT. If more
accurate volumes are required a 24-hour count should be made.
NEW ROAD
Primary and Determine/analyze the design ADT for new road using area demographics and travel patterns, determine the redistribution of existing traffic
Secondary Roads volumes and traffic volumes generated by new development that will use the new road(s).
Conduct Roadside Interview Origin Destination Surveys to estimate the directional distribution of traffic.
Local Streets 12-hour manual counts taken from 6 a.m. to 6 p.m. on Sunday or Wednesday, Monday and Tuesday. Total hourly volumes shall be recorded.
Convert to 24-hour ADT by multiplying the 12-hour volume by 2. This will provide a conservative estimate of the 24-hour ADT. If more
accurate volumes are required a 24-hour count should be made.
FOR ALL TRAFFIC COUNTS
1. Counts shall not be taken on special holidays or during events which occur once per year.
2. Counters shall be placed at points of obvious traffic volume changes
3. Manual counts shall be taken at the same place(s) as machine counts. Manual counts shall be used to verify machine counts.
4. Manual and machine counts shall be performed for each direction.
Part 1 200-16
ROADWAY DESIGN MANUAL Roads and Bridges
Table 200.07
Summary of Datums Used In Abu Dhabi
Reference Level Admiralty Chart Admiralty Chart Abu Dhabi Datums Abu Dhabi Datums Sauti Datums
Datums Datums Old New
Existing Corrected
Meters Feet Meters Feet Meters Feet Meters Feet Meters Feet
Bench Mark on Plinth of ADPC 3.20 10.50 3.50 11.48 2.15 7.05 2.20 7.22 1.90 6.23
Building
Mean Higher High Water at 1.89 6.20 2.19 7.18 0.84 2.76 0.89 2.92 0.59 1.94
Springs near Solstices
Mean Higher High Water 1.56 5.12 1.86 6.10 0.51 1.67 0.56 1.84 0.26 0.85
Sauti Datums 1.30 4.27 1.60 5.25 0.25 0.82 0.30 0.98 0.00 0.00
Mean Lower High Water 1.19 3.90 1.49 4.89 0.14 0.46 0.19 0.62 -0.11 -0.36
Mean Sea Level 0.95 3.12 1.25 4.10 -0.10 -0.33 -0.05 -0.16 -0.35 -1.15
Abu Dhabi Old Datums 1.05 3.44 1.35 4.43 0.00 0.00 0.05 0.16 -0.25 -0.82
Abu Dhabi New Datums 1.00 3.28 1.30 4.26 -0.05 -0.16 0.00 0.00 -0.30 -0.98
Mean Higher Low Water 0.80 2.62 1.10 3.61 -0.25 -0.82 -0.20 -0.66 -0.50 -1.64
Mean Lower Low Water 0.25 0.82 0.55 1.80 -0.80 -2.62 -0.75 -2.46 -1.05 -3.44
Admiralty Chart Datums Existing 0.00 0.00 0.30 0.98 -1.05 -3.44 -1.00 -3.28 -1.30 -4.27
Mean Lower Low Water at -0.18 -0.59 0.12 0.39 -1.23 -4.04 -1.18 -3.87 -1.48 -4.86
Spring Near Solstices
Admiralty Chart Datums -0.30 -0.98 0.00 0.00 -1.35 -4.43 -1.30 -4.27 -1.60 -5.25
Corrected
Part 1 200-17
ROADWAY DESIGN MANUAL Roads and Bridges
ENVIRONMENTAL CHECKLIST
Project: Date:
Part 1 200-18
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-19
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-20
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 200-21
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Part 1 300-1
ROADWAY DESIGN MANUAL Roads and Bridges
Project Location
Final Report
Project No.
15 May 1997
Prepared by
De Leuw Cather & Co. Client Prepared for
Preparers th
3875 N. 44 Street, Suite 250 Logo
Logo
Phoenix, AZ 85018 Abu Dhabi Municipality
Figure 300.01
Standard Design Concept Report
Cover Sheet
Part 1 300-2
ROADWAY DESIGN MANUAL Roads and Bridges
The horizontal alternative alignments will be the minimum design speed(s), min.
displayed on aerial photographs for evaluation of horizontal/vertical curve radii, sight min.
associated impacts. The sheets will show the distance (passing and stopping), max.
proposed centerline, stationing, proposed superelevation and other design requirements
structures, edge of pavement lines and affected associated with the classification of the road;
properties, at a scale that is appropriate to the the actual design speed(s), horizontal/vertical
project length and character. curve radii, sight distance (passing and
stopping), superelevation, etc. used for the
A cost estimate will be prepared for each project;
alternative and include: lane width, shoulder width, and bridge width;
on the project
Construction costs cross slope;
Utility relocation works costs grade;
Land acquisition costs horizontal and vertical alignment (actual);
horizontal and vertical clearance; and,
At this point, meetings will be held with various bridge structural capacity.
Municipality and Government Departments that
have a vested interest in the project. The engineer The design exceptions identified shall be prepared
will present the alternatives, review the evaluation in a Fact Sheet format as described in Part 2,
criteria and matrix form and discuss merits and Section 100, General Design Criteria.
adversities of the different alternatives.
Comments and direction received at the 307 TYPICAL SECTIONS
meeting(s) will be factored into the alternatives
evaluation matrix. The typical roadway cross sections and the
dimensions of the lanes, shoulders, median(s) for
Finally, the analysis will conclude with a both the mainline and all ramps are to be
discussion of the evaluation criteria for each identified. The number of typical sections will
matrix parameter, input/direction received depend on the number of significantly different
concerning the project and a summary discussion roadway/pavement structure conditions. At a
of the advantages and disadvantages of each minimum, at least one section should be provided
alternative studied. This will be followed by the which depicts all facilities within the limits of the
engineers recommended alternative with right-of-way (i.e., ramps, frontage roads, drainage
supporting justification for the selection. channels, etc.).
306 DESIGN DATA The type of roadway section, i.e., cut or fill,
number of lanes, shoulders, pavement structural
This section will document the design criteria section, cross slopes, and any retaining walls are
associated with the recommended design concept also to be included. Drawings that illustrate this
and specifically identify any exceptions from the information are to be included in the Appendix to
minimum criteria established for the roadway the DCR.
classification.
308 GEOMETRICS
It is very important that sufficient detail is
included in the DCR so that future revisions to The alignment, profile, and number of traffic
basic design features and project scope are held to lanes, including through lanes, auxiliary lanes,
a minimum. turning lanes and ramp lanes are to be plotted on
an appropriately scaled plan. A scale of 1:500
The following basic design criteria established in should be used for urban projects and 1:2500 for
Part 2, Roadway Design, shall be included: rural projects. The alignment should be displayed
on an aerial base and the corresponding roadway
the functional classification of the road per profile shown below in a split sheet format.
Part 1, Section 100, General Information.
Part 1 300-4
ROADWAY DESIGN MANUAL Roads and Bridges
The text in this section should include a narrative The results of the study shall be summarized in
description of the geometrics, constraints, the body of the DCR, with the entire study
controlling factors, drainage considerations and included in the Appendix.
reference to the design exceptions. The plans are
to be attached as an appendix to the DCR. The summary of the results shall include:
Part 1 300-5
ROADWAY DESIGN MANUAL Roads and Bridges
systems (pipes and channels including flow 311.02 PLANNING & PREPARATION OF
direction, sizes and peak flow volume) THE DRAINAGE DESIGN
CONCEPTS
Hydrology calculations for drainage area
intercepted by the project to include peak The Municipality often is and should be perceived
runoff volume flow rates from each drainage as a developer of transportation facilities that
area have the potential to stimulate secondary activity
along the transportation corridor just as a major
Proposed concepts for disposal of storm residential development can stimulate commercial
water. activity. Accordingly, there is a requirement to
address overall stormwater management needs in
Design criteria, procedures, methodology, and conjunction with existing and future developments
assumptions for analysis and design. planned for the foreseeable future. Because the
transportation corridor often traverses several
Proposed concepts for handling and disposing watersheds, the development of an adequate
of storm water during construction. stormwater management plan can be severely
fragmented and significant problems created if
Recommended size and location of cross there is a lack of coordinated planning among
drainage structures and channels, including concerned parties.
design high water elevation that might affect
the road profile grades or the roadway To be truly effective, a stormwater management
location. plan should consider the total scope of
development (i.e. transportation, residential,
Proposed concepts for on-site roadway commercial, industrial and agricultural).
drainage collection, detention, and outfall Department coordination with responsible
locations. Agencies and other Departments is essential to
ensure that proposed facilities match existing
ones, and that they are consistent with the long-
Separate Flood Plain Study Report where the
term needs of the area. Significant savings can
roadway encroaches on flood plains either
often be realised by planning overall combined
longitudinally or transversely.
stormwater management facilities, even though
the roadway development is only a small part of
Bridge Location and Hydraulics Report for
the total system. In addition, the Municipality can
bridge or large box culvert waterway
provide important information to other Agencies
crossings.
and private developers wishing to develop a
comprehensive stormwater management plan
311.01 PURPOSE
without assuming responsibility for the planning
and decision making process for the entire
The purpose of the drainage design concept study
watershed.
is to document the methodology and results of the
hydrologic analysis and the rationale used in
Accordingly, prior to design, a level of planning
developing the roadway drainage system. It shall
and coordination shall be undertaken by the
define the type, size, and location of cross
designers that will properly locate facilities and
drainage structures and channels, and determine
adequately address the overall drainage needs of
flood level elevations.
the overall watershed(s) in regards to existing and
future (foreseeable planning) development. This
The drainage design concept study shall determine
section provides general guidelines and major
the initial type, size and location of the onsite
considerations for evaluating these factors during
roadway drainage system and determine outfall
the planning process.
location(s). It shall also address any floodplain
encroachments and the overall watershed
planning.
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ROADWAY DESIGN MANUAL Roads and Bridges
These are further defined as follows: Quantification of the levels of contaminants that
are being washed off a roadway is complicated by
A. Quality: Several broad categories of the variable effects of and the periods between
degradation have been developed to delineate or storm events. The contributory factors are rainfall
describe levels of stormwater impacts: intensity, street surface characteristics, and
particle size. The varying interaction of these
Aesthetic deterioration: Undesirable general factors makes it difficult to precisely estimate the
appearance features (dirty, turbid, or cloudy) impact that discharge will have on water quality.
and actual physical features (odors, floating
debris, oil films, scum, or slime) are present. However, where it is suspected that periodic
runoff may have a serious quality effect upon the
receiving area, further investigation, analysis and
Dissolved oxygen depletion: When the oxygen
methods for solving the problem should be
demand of bacteria is stimulated by the
presented for review and approval.
organics, the subsequent reduction in oxygen
levels can disturb the balance between lower
The quality control management procedure
forms and the food chain. Unoxidized
particularly applicable to this region would
nitrogen compounds (ammonia) can also
consist of diverting the first 8 to 10 millimeters of
cause problems. This is of concern when
runoff into retention (often combined with
discharging into reservoirs, small, limited
detention for peak quantity control) basins where
flush, tidewater areas, and freshwater
the more concentrated contaminates and
streams.
sediments can be contained. The volume of
stormwater is then allowed to dissipate slowly by
Pathogen concentrations: High concentrations
seepage and evaporation, effectively trapping the
of several pathogens can reduce the
contaminates in the basin for periodic cleanout
acceptable users of the receiving waters. A
and disposal in a sanitary land-fill as needed.
concern where discharge may be accessed for
domestic use and discharge near public use
An exception is erosion and sediment control,
areas (bathing beach).
which is often a significant component of
stormwater quality. In general, erosion and
Suspended solids: The physical build-up of
sediment transport should be limited by
solids can cover productive bottoms, be
Part 1 300-7
ROADWAY DESIGN MANUAL Roads and Bridges
developing and implementing an erosion and 3. Will the project require retention or detention
sediment control plan which addresses both storage areas to mitigate the impacts of
temporary and permanent control practices. increased runoff, or can the increase be
handled by other project features?
B. Quantity: Determinations of stormwater
quantity are primarily useful for evaluating and 4. Is there sufficient area to construct a retention
mitigating the impact of a project. Without or detention storage within the project limits?
detention, land development increases peak runoff Are alternative sites available for storage of
rates and volumes from storm events, which can stormwater?
lead to higher flood elevations. Appropriate
hydrologic and hydraulic calculations presented in 5. What are the groundwater and soil
various chapters of this manual should be made to conditions? Is there a high groundwater
determine the required conveyance through the table, or are there impermeable soil layers?
Municipalitys project limits, and to aid in
mitigating impacts to downstream structures and C. Flood Plain Encroachment: The primary
development. drainage consideration for facility location in
highway planning is the evaluation of the impact
Procedures contained in Part 2, Section 700, of flood plain encroachment for a steam or wadi
Roadway Drainage Design, should be used to crossing or where the road embankment
evaluate the ability of a facility to accomplish the longitudinally encroaches into the flood plain
following controls for a particular area: area.
Provide positive drainage and runoff The following factors for locating a stream
collection to the minimum criteria for safe crossing that involves encroachment within a
passage of traffic on the project roads and flood plain area:
parkings.
Waterway characteristics (stable or
Reduce runoff rates when applicable by unstable)
increasing infiltration, and by storing Geometry
precipitation and runoff where it falls and Hydrology
releasing it slowly. Hydraulics
Alignment
Protect areas subject to flood damages by Flood plain flow
keeping runoff confined to drainage facilities Needs of the area
such as pipes or channels and by building Economic and environmental concerns
appropriate flood control facilities.
A detailed evaluation of these factors is part of
Maintain offsite flows, through the project the bridge location and hydraulics study. When a
area. suitable crossing location has been selected,
specific crossing components can then be
Limit flood plain enroachment to acceptable determined. When necessary, these include the
upstream/downstream flooding impacts. geometry and length of the approaches to the
crossing, the probable type and approximate
The following questions should be considered location of the abutments, the probable number
when selecting the plan for disposal of stormwater and approximate location of the piers, the
runoff: estimated depth to the footing supporting the piers
1. Are existing drainage systems large enough to (to protect against local scour), the location of the
handle runoff? longitudinal encroachment in the flood plain, the
amount of allowable longitudinal encroachment
2. Are runoff estimates consistent with adopted into the main channel, and the required river
drainage plans and Municipality criteria? training works, to ensure that river flows
approach the crossing or the encroachment in a
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ROADWAY DESIGN MANUAL Roads and Bridges
complementary way. Exact information on these before and after the proposed project in both the
components is usually not developed until the upstream and downstream directions for a
final design stage. distance to where it can be shown that no further
impact over pre-project conditions is influenced
Where the roadway embankment encroaches by the project for: (i) the design event storm, (ii)
significantly in a longitudinal direction into the for the 100 year storm, and (iii) the maximum
flood plain, a separate floodplain encroachment probable storm (usually the 500 year event).
study must be made to evaluate the increased Besides the peak water surface profile, the
flood depths and velocities that may impact, analysis shall include the flow volumes, velocity
upstream and down stream properties. profiles (velocity at various points in the cross-
section), and hydraulic structural alternatives that
Further details defining flood plain encroachment were evaluated to mitigate significant
are provided in Section 311.02.02. encroachment.
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ROADWAY DESIGN MANUAL Roads and Bridges
limitations, and limiting velocity are parameters constraints would be the preferred design. This
for which design standards can be set. design should then be investigated for the 100-
year flood.
Two other approaches, however, are available
that quantify risk on projects that involve 311.02.03 Data Collection
highway facilities designed to encroach within the
limits of a flood plain. These are risk assessment Identification of drainage data needs should be a
and economic analysis. Risk assessment is a part of the early planning phase of a project,
subjective analysis of the risks engendered by when appropriate procedures for performing
various design alternatives, without detailed hydrologic and hydraulic calculations are
quantification of flood risks and losses. It may selected. Several categories of data may be
consist of developing the construction costs for relevant to a particular drainage project, including
each alternative and subjectively comparing the published data such as precipitation, soils, land
risks associated with each alternative. Economic use, topography, streamflow and flood history.
analysis (sometimes called risk analysis) Published mapping is usually inadequate, so field
encompasses a complete evaluation of all investigations and surveys are necessary to
quantifiable flood losses and the costs associated determine drainage areas, identify pertinent
with them for each structure alternative. This can features, obtain high water information, survey
include damage to structures, embankments, lateral ditch alignments and survey bridge and
surrounding property, traffic-related losses and culvert crossings. In addition, hydrology
scour or stream channel change. The level of calculations for a watershed or larger drainage
expense and effort required for an economic area will usually require some sort of topographic
analysis is considerably higher than for a risk mapping. The preferred mapping is using aerial
assessment, and selection of the process to be photography showing contour elevations using
used should be based on the size of the project digital techniques is preferred. Manual ground
and the potential risk involved. A risk assessment surveys are usually adequate for smaller areas.
is usually more appropriate for small structures The requirements in more detail are as follows:
or for structures whose size is highly influenced
by non-hydraulic constraints. A. Data Collection Procedure: Drainage data
should be collected before calculations are
Policy dictates that hydraulic facilities be initiated, under the following general guidelines:
designed so that highway facilities will perform
without significant damage or hazard to people or 1. Identify data needs, sources, and uses. Much
property during the appropriate standard design of this information will have to be provided in
frequency flood. Risks associated with floods of the concept report and kept in the supporting
magnitudes greater than the standard design files.
frequency flood should be evaluated in
accordance with the risk evaluation levels 2. Collect published data, based on sources
presented in this section. If warranted, a design identified in Step 1.
based on a lower or higher frequency flood may
be used. The minimum design frequency for 3. Compile and document the results of Step 2,
bridges on main highways, however, is 50 years. and compare data needs and uses with
published data availability. Identify any
A typical example would be a major cross drain additional field data needs.
box culvert for a primary highway. The standard
design frequency would be a 50-year frequency 4. Collect field data based on needs identified in
flood. A design based on this frequency should Steps 1 and 3.
be produced in the "traditional" manner, including
development of feasible alternatives. The 5. Compile and document the results of Step 4.
alternatives would be compared for cost and for
risks associated with the 50-year frequency flood. B. Published Data: At present, there is limited
The lowest total cost structure that met the design published data with regards to soils, land use,
Part 1 300-10
ROADWAY DESIGN MANUAL Roads and Bridges
streamflow, flow histories, etc; however, a For urban type construction surveys, appropriate
thorough search for soils investigation records city maps or specially prepared maps should be
and existing utility/drainage systems should be marked to show the boundaries of total areas
made from as-builts of other projects in the contributing to the project. Streets or other
vicinity. Old newspaper records may also be a drainage facilities in these areas should be marked
source of timing and pictures of past flooding with flow arrows. In many instances, elevations
events. may have to be determined to accurately delineate
direction of flow in gutters or side of road
C. Drainage Areas: If there is sufficient channels.
topographic information for a project site from
readily available sources (aerial mapping), a field All areas contributing to existing storm drains
determination of drainage area may not be which drain to or across the project should be
necessary, but spot-checking selected control shown. In very flat terrain, it is often necessary
elevations is always advised. For those project to develop profiles for cross streets and parallel
sites for which detailed information is not streets to make a definite determination of
available, field survey work or aerial photo drainage areas.
mapping should be performed. In all cases, a site
visit by the designer is mandatory to confirm Specially flown aerial photography should be
drainage area conditions. obtained for most construction projects.
Elevation contours and ridge lines usually can be
Drainage areas shall be outlined on the drainage indicated on the photographs utilizing digitized
map (preferably on a contoured photo base map). cartography combined with ground based control
Drainage area boundaries should connect with the surveys. When photographs are used, the field
job centerline, typically at high points in grade or survey party should verify questionable points
at other locations where there is a definite division and supplement the information with structure
in the direction of storm runoff flow. After the sizes, elevations, and elevations as required.
overall areas are plotted, the drainage area should Drainage areas can also be determined by stereo
be sub-divided to show how the various sections interpretation of stereo paired photographs with
contribute to the structures in the proposed spot field survey work as appropriate (usually
drainage or storm drain system. sufficient for smaller areas).
All drainage area boundaries should be followed D. Drainage Maps: For roadway projects, the
from project centerline around the area being drainage maps should be prepared on pre-
covered and closed again to the roadway formatted sheets that use a cross section grid
centerline. Ridges that do not establish an area printed across the lower portion for plotting the
draining to the project should not be shown unless project profile. The profile is plotted to some
pertinent to determination of runoff concentration convenient scale according to need. For projects
points or flow path segments. Exceptions to the involving interchanges, rest areas, urban streets
rule for closing all drainage area boundaries to and the like, a supplemental drainage map that
centerline are to be indicated clearly on the map shows only the plan portion on a sheet without a
by notation. These notations should show profile grid is required. The supplemental map is
location and elevation of breakover or diversion to provided to show the small areas needed to
or from the drainage area. calculate pipe sizes for the tabulation of drainage
structures within these special areas.
Typically, a drainage area should close to each
existing culvert along the project, for each The following data should be provided on the plan
probable cross drain location to each inlet for portion of the map:
piped system, and protected overland flow
entrances to channels. As an exception, where 1. Physical land features affecting drainage,
two or more structures operate conjunctively to such as elevation contours, land use,
drain a single area, flow distribution information vegetation cover, streams, wadis, reservoirs
should be noted. and tidal areas, together with past high water
Part 1 300-11
ROADWAY DESIGN MANUAL Roads and Bridges
and date of occurrence, if available, and 6. In the report, the various cross-drain
present water elevations with the dates of the culverts should be summarized by station,
readings, as appropriate. size, invert elevation and minimum culvert
backfill values for pH, resistivity, sulphates,
2. Existing drainage structures, showing type, and chlorides for the various alternate
size, flow line, flow direction, and any other culvert materials.
pertinent data.
The profile portion of the map should include the
3. Drainage divides and information, where following data:
applicable, to indicate the overland flow of
water. Drainage areas on maps of urban and 1. Plot of the existing ground, done in a light
rural sections should be shown to the solid line to the same horizontal scale as was
accuracy necessary, depending on the system used for the plan portion.
involved. A guide to the appropriate
accuracy for a non-critical system is 2. Drainage map sheets with the profile blocks
provided. Critical systems usually require a deep enough to sufficiently show the
drainage area determination within 2 to 3 necessary profiles and cross-drain profiles.
percent.
3. Plot of the proposed profile grade line.
Part 1 300-12
ROADWAY DESIGN MANUAL Roads and Bridges
spiral) and size of corrugation. Flow line any location where water comes to and/or leaves a
elevations of pipes should be shown at both inlet proposed project. They should clearly show the
and outlet. For box culverts to be extended, an path and approximate elevations of flow for
accurate sketch should be made showing the size existing ditches and natural streams. Inflow data
and length of the culvert, thickness of all walls, should be provided for a distance sufficient to
wings, and slabs, and the angle of the barrel with indicate the degree of channelization and the
the survey centreline. Elevations should be given direction of flow, usually a distance of 30 to 100
on the top of the bottom slab, top and bottom of meters.
top slab, parapet walls, wings, etc., on each end
of the culvert. Data on the outfall portion should extend far
enough to determine the direction and degree of
The type, length and width of roadway, location channelization and the rate of fall in water
of bents, number of piles per bent and type of surface, and to reach a point of positive and safe
footings should be shown for bridges in place. disposal. If ditch or channel work appears
Profiles should be shown as centerline of necessary, collection of topographic data should
roadway, from the edge of pavement left and right continue downstream to a point at which damage
of centerline of survey, and under the bridge on to adjacent property appears to be insignificant.
centerline of survey. The profiles should
accurately define the top and bottom of channel If the length of an outfall raises serious doubts
banks and the channel bottom. about its usefulness, the field party should
terminate the survey at 150 meters and note the
2. High Water Information: Reliable high approximate distance to a suitable disposal point.
water information is necessary to evaluate flood This note should give the distance, the water
elevations and establish roadway grades. High elevation at the approximate end, and a brief
water elevations should be shown upstream of the description of the topography (i.e., tidal bay,
proposed project, upstream of significant existing reservoir, wadi, etc.) into which the outfall will
structures, and at some point along or at the end drain if extended. The designers can then
of outfall ditch surveys. The location at which a determine if a further detailed outfall survey is
high water elevation is taken should be clearly required.
recorded in the field notes, along with the date and
time if available. The field survey for a lateral ditch should always
include property boundaries or plot walls/fences,
At many locations, it is not possible to obtain which are often the determining factors in the
documents information on high water. In such ultimate location of outfalls. With property
cases, elevation may be estimated by observation boundaries marked, the design engineer is in a
of natural growth, evasion marks or by other much better position to determine the extent of
means. The survey crew should provide complete cross-sectioning needed to cover possible
information on the methods used. The crew chief alterations in alignment, and the design engineer
should attempt to obtain information from local is aware of the limitations in changes he may
residents or maintenance personnel. consider.
The soils investigation usually supplies water 4. Bridge and Large Culvert Surveys:
table information within the project limits; Locations of larger culverts and bridges often
however, the survey crew should note information must be detailed. The meander of both banks of a
pertaining to standing water, areas of heavy stream for a sufficient distance upstream and
seepage, or springs within the basin area. downstream to determine the approximate extent
of any probable channel relocation should be
3. Lateral Ditch Surveys: Most highway section obtained. This ordinarily can be shown within
projects should routinely include lateral ditch 150 meters upstream and downstream from the
surveys at the locations of existing ditches, project. Any major overflow channels also should
streams, wadis, swales, etc. The surveys should be indicated within approximately the same limits
provide a clear picture of existing conditions at or within the limits that these channels leave and
Part 1 300-13
ROADWAY DESIGN MANUAL Roads and Bridges
return to the main channel. Meandering channels Field surveys at existing bridges should include
close to and approximately parallel to the project three profiles: the first on the survey centerline,
centerline should be located carefully and cross- the second approximately 10 meters right of the
sectioned. survey centerline, and the third approximately 10
meters left of the survey centerline. The purpose
Across flood plains where the proposed project of the second and third profiles is to provide data
follows an existing fill, cross-sections should at the edge of the bridge. The centerline profile
extend far enough to provide a record of natural should show the roadway grades and the ground
ground profiles right and left of the project. Any line under the bridge. Cross-sections should be
washouts or significant swales, side wadiis, taken across the bridge area to furnish elevations
sloughs or ditch outlets should be noted clearly in for plotting the face of the slopes and for accurate
the topography. plotting of low water channels. All profiles
should include points indicating the top of the low
Recommendations for significant realignment or water banks (the edges of the low water channel),
improvement of an existing channel often will water level at the date of the survey, and the
come as part of the structure design, making it profile of the stream bed along the survey lines.
necessary to survey a designated location. For Where new lanes for the roadway are to be
this reason, specific channel location surveys located at bridges from a survey along the old
should not be made during the initial location roadway using cross-sections for approximate
survey unless the need for and logical location of elevations, it is necessary that the three profiles be
such changes are apparent. run along each side of the new roadway,
furnishing complete channel limits and elevations
Required data on existing roadway and railroad on each profile. These surveys should include
structures upstream and downstream should be corrected stationing referenced to the road survey,
identified by the drainage engineer so it can be showing station and elevation equalities if
included in the survey. For fills and structures in necessary. At expressways, where a single profile
reasonable proximity to the project, a profile of is run along the centerline of the median for the
the existing roadway showing structure openings roadway survey, the three profiles and cross-
should be established relative to the project data. sections should be performed for each lane at all
For structures farther removed, it is often bridges.
adequate to include only a profile and high water
information. The information should include 5. Documentation: Documentation involves the
observations on scour, washouts, or other compilation and presentation of all pertinent
pertinent hydraulic factors. Where scour is watershed data collected for the project. It should
significant, cross-sections should be taken to include (but is not limited to) basic items such as
determine the depth and extent. drainage area and other maps, field survey
information, published data references,
Appropriate flood elevation data should be photographs, and narratives from witnesses of
obtained for bridges. If reliable data is not historic floods. This data should be maintained in
available, that fact should be noted by the field the permanent records. The orderly compilation
party. The extreme high water, its location, and and presentation of watershed data will expedite
the approximate date of its occurrence should be the design, review, and evaluation phases of a
recorded, if available. Other elevation high water drainage project
that can be dated should also be recorded when
practical. If possible, a "normal" high water 311.03 STORM WATER HYDROLOGY
elevation, or one which can be expected to recur
about every 2 to 3 years, should be determined. To convert precipitation to stormwater runoff,
A normal elevation that would be expected to hydrologic calculations are generally used to
prevail through seasons of average rainfall should quantify the abstractions (precipitation losses)
be recorded. which occur as part of the hydrologic cycle.
Virtually all drainage and flood plain calculations
only consider infiltration, interception, and
Part 1 300-14
ROADWAY DESIGN MANUAL Roads and Bridges
surface storage losses, since short time scales will 7. Perform downstream channel and reservoir
usually render losses from evaporation and routings, as appropriate.
transpiration insignificant. A possible exception
to this usage is for land-locked watersheds. 8. Record the necessary calculation process
and the results on the appropriate drainage
Since the governing relationships of hydrology are maps, and in the drainage section of the
complex and, unlike problems in engineering Design Concept Report, as appropriate.
mechanics, are not easily solved through direct
use of the fundamental laws of physics, a wide 311.04 OPEN CHANNEL HYDRAULICS
variety of hydrologic procedures have been
developed. Procedures for making time of The consideration of open channel hydraulics is
concentration and rainfall excess calculations, an integral part of roadway projects in which
procedures for estimating peak runoff rates at artificial channels and improvements to natural
gaged and ungaged sites, procedures for channels are a primary concern. Procedures for
developing design storm hyetographs, and flood performing uniform flow calculations that aid in
hydrograph and hydrologic channel routing the selection or evaluation of appropriate channel
procedures are contained in the drainage volume linings, depths, and grades are included in the
of the design manual. drainage volume of the design manual. For most
artificial channels, the most desirable lining is
Drainage studies often follow a similar sequence natural, emerging vegetation, with grass used to
of calculations for all procedures, because provide initial and long-term erosion resistance.
precipitation must be routed through watersheds, If natural vegetation, usually grass, is unfeasible,
channels, and reservoirs. In most cases, concrete lining is used. Also, flexible linings
stormwater runoff will be estimated using the comprised of rock riprap asphalt or articulating
following general procedure: concrete grids can be used for preventing erosion.
Allowable velocities and permissible depths of
1. Divide the watershed into appropriate flow are provided in the drainage volume of the
subareas to correspond with homogeneous design manual, along with various adaptations of
land use conditions and the placement of Manning's Equation suitable for evaluating
drainage facilities such as inlets, reservoirs, channel capacity.
and open channels.
Open channels can be generally classified as those
2. Collect and analyze watershed data. which occur naturally and those which are man-
made or improved natural channels. The later,
3. Establish design storm conditions as called artificial channels, include the following
appropriate for the procedure selected. types in use on most roadway project:
4. Calculate the peak runoff rate or determine 1. Right-of-way ditches which usually acts as
the time distribution of rainfall excess. No an overland flow interceptor ditch collecting
further calculations are generally required if water before it reaches the roadway.
only the peak runoff rate is desired. 2. Roadside or roadway ditch and (sometime
called the borrow ditch)
5. Develop a unit hydrograph for the 3. Median ditches on divided highway.
watershed, if a runoff hydrograph is desired 4. Outfall ditches for connecting and carrying
and the procedure selected uses a unit flows from ditch types 1, 2 and 3, a short
hydrograph. distance to a natural outlet or to another,
larger conveyance channel.
6. Develop the direct runoff hydrograph, using 5. Lateral ditches are a larger size channel,
the unit hydrograph and rainfall excess usually used for continuing upstream flows
determined above, as appropriate. past the project area.
6. Canals are large size conveyance channels.
Part 1 300-15
ROADWAY DESIGN MANUAL Roads and Bridges
Each of these channel types are artificial systems 311.05.01 Bridge Location and Hydraulics
designed to provide specific drainage capacities. Report
The right-of-way ditch functions as a type of
relief ditch, handling drainage needs other than A. Documentation: Documentation shall be
those for the roadway and thus freeing roadside provided in detail commensurate with the
ditches from carrying anything except roadway complexity of the project. Documentation shall
runoff. Right-of-way ditches can also act as be sufficient enough so that an independent
interceptor ditches to provide a method for engineer with expertise in bridge hydraulics, but
intercepting offsite flows or subsurface not involved with the design, can fully interpret,
groundwater flows above cut slopes, thereby follow and understand the logic, methods,
controlling slope erosion. computations, analysis and considerations used to
develop the final design.
In general, roadside or median ditches are
relatively shallow trapezoidal channels or swales Documentation for bridge and large culvert
(which are shallow triangular channels). Both designs shall include as a minimum the following:
types are designed to handle local surface runoff
from roadway surfaces, or to lower water table 1. Hydrologic analysis including sources of data
elevations by intercepting groundwater. In some and methodology.
cases, they may also handle other than project
drainage. Outfall ditches or canals are designed 2. Alternative analysis or evaluation of structure
in most cases as receptors of runoff from sizes (length and vertical height/clearance).
numerous secondary drainage facilities, such as This evaluation shall be done consistent with
side ditches or storm drains. The use of a Department criteria for bridge hydraulic
roadside ditch as an outfall ditch is not design and shall include consideration of:
recommended, since its probable depth and size
could create a potential hazard. a. cost
b. design standards
311.05 BRIDGE HYDRAULICS c. structure hydraulic performance,
including backwater, velocity and scour
Bridge hydraulic designs shall be documented in d. Impacts of the structure on adjacent
the Bridge Location and Hydraulics Report property
(BLHR). Design information shall be e. environmental impacts
summarised on the Bridge Hydraulics
Recommendations Sheet (BHRS). The format for 3. The alternative analysis shall include the
the BHRS is provided in Section 3.11. reasons for selecting the recommended
structure and a clear explanation as to why it
BLHR and the BHRS shall be prepared for the is the most economical structure for the site in
projects listed below: question. As a minimum, the following
structure sizes shall be evaluated:
1. Bridges and large culverts (culverts larger
than 1800 mm dia pipes or 1200 mm x a. The minimum structure size required to
1200m box culverts) on new alignments meet hydraulic standards for vertical and
2. Bridge and large culvert replacements on horizontal clearance, scour and
existing alignments backwater.
3. For other bridge and large culvert projects b. Existing structure size if applicable.
involving actions within the Base Flood c. The recommended structure size if
Plain (work within the 100 yr. Flood different from (a) or (b).
elevation) e.g., bridge widening and large
culvert extensions. 4. Design recommendations for bridges
recommendations shall include:
Part 1 300-16
ROADWAY DESIGN MANUAL Roads and Bridges
a. Bridge length, and justification for the the subsections identified below. Rather than a
length, including locations (stations) of formal item by item approach, a narrative
abutments description of the site and the hydraulics
b. Channel excavation requirements recommendations is suggested.
c. Minimum vertical clearance
d. Minimum horizontal clearance Preliminary Information
e. Abutment type and orientation
f. Pier orientation A. General Site Location
g. Scour depths for the design flood, 100-
year flood and maximum probable flood 1. Highway Description
(usually the 500-year flood).
h. Scour protection requirements for a. Type (expressway, main, secondary,
abutments, piers and channel rural, urban, etc.)
i. Deck drainage b. Lanes (two, four, divided, limited across,
etc.)
5. Documentation of large culvert hydraulic c. Importance (main access between towns
designs shall include hydraulic calculations and borders, military route, alternate
and recommendations for the following: routes available, etc.)
a. Culvert Size, and justification for the 2. Topography of site and basin
size, barrel length and location 3. Location: small scale map with site located
b. Peak water surface profiles and cross-
section velocity profiles for the design B. Potential Site Problems
flood, the 100 yr flood and the maximum
probable flood for a distance 150 meters 1. Land Use (obtain from responsible
upstream, through the culvert to a Department)
distance 150 metres downstream.
c. Upstream and downstream invert a. Encroachment on the flood plain
elevations. b. Recreational use
d. Endwall type for entrance and outlet, c. Domestic water supply
including the need for an improved inlet. d. Security area
e. Skew
f. Inlet end and outlet end scour protection 2. Channel Stability
requirements
a. Bank stability
6. Final project plans shall show the peak b. Bends and meanders
stages, peak discharges, peak velocities, and c. Potential for natural change of channel
peak scour predictions for the design flood, d. Aggradation or degradation of bottom
the 100 year flood and the maximum e. Scour history
probable flood that can be expected to flow
through the structure. 3. Potential Water Stages
B. Report Outline: An outline of items that a. Flood history (dates; stages; source of
should typically be considered in the preparation information; extent of flooding;
of a BLHR is given below. Non-applicable items approximate frequency; damage to
should be so indicated rather than omitted without structure, embankment or highway)
comment. Additional information may be b. Potential backwater from other streams
appropriate at unusual sites. or rivers
c. Reservoirs of flood control projects
The BLHLR should be divided into two basic (Department and status)
sections: Preliminary Information and Design d. Tidally affected (mean high and low
Data. These sections are then broken down into water)
Part 1 300-17
ROADWAY DESIGN MANUAL Roads and Bridges
Part 1 300-18
ROADWAY DESIGN MANUAL Roads and Bridges
E. Additional Survey Data of Proposed Site design flood, the base (or 100-year) flood, and
either the overtopping or maximum probable
1. Data sufficient to prepare a contour map flood, whichever occurs first. The overtopping
(intervals at 30 cm or 60 cm depending on flood is the one in which flow crosses the
scale); required distance upstream and highway, or spills into another watershed or
downstream will vary with site through a relief structure. The max. probable
2. In lieu of (1), a minimum of three cross flood is normally a 500-year event. Flood data
sections will suffice for some cases includes stage elevation, discharge, average
(upstream, at, and downstream of site) velocity (on larger crossings a velocity profile
3. Vegetation, estimated bed load, bottom soil across key cross-section is usually needed) and
material and soil properties, and other general exceedance probability.
site parameters
Water surface elevations are classified as normal
F. Departmental Coordination high water for non-tidal areas and as mean low
and mean high water for tide-influenced areas.
1. Contact Departments involved and identify Normal high water is defined as the 2-year event;
what other projects may be affected by the mean low water and mean high water data can be
culvert/bridge obtained from the admiralty charts.
2. Investigate possibility or necessity for a
cooperative project Hydraulic recommendations should include the
beginning and ending bridge stations, data on the
It is also suggested that a checklist of required channel section (including any excavation),
items for each site be prepared and given to the navigation and drift clearances, scour prediction,
survey crew to ensure complete data will be slope protection, and deck drainage.
obtained with a minimum of supplemental or
unnecessary effort. Space should be provided for a small scale
location map outlining the drainage area. A plan
311.05.02 Bridge Hydraulics view of the existing and proposed bridge area
Recommendations Sheet (BHRS) must also be included. The scale should
adequately depict the area adjacent to the
The BLHR is a full size drawing, to be included structure, including existing and proposed
with the BLHR. It is divided into several contours. Drainage areas for very flat sites
information blocks, which must be as completely warrant careful delineation since only one or two
filled out as is appropriate for the design and contours may occur. For a bridge, a profile of the
location. The BHRS must always include the channel section should be shown; for a large
Project Number and the Bridge Number as per culvert, the culvert centreline should be profiled.
the drainage map in the title box. The profile should show channel work and bridge
end treatment. If necessary for clarity, bridge
The information requested for existing bridge or ends should be drawn at a larger scale.
large culverts near the site includes foundations, The assumed configuration, deck drainage, and
overall length, span length, type of construction, scour recommendations need to be approved by
area of opening at high water, roadway width, the Municipality before plans are completed.
and the low member elevation. The area of This review provides an opportunity to evaluate
opening at high water generally refers to the flow the impact of substantial changes on the hydraulic
area available through the existing structure design conditions.
below the water surface determined for a design
storm frequency.
Part 1 300-19
ROADWAY DESIGN MANUAL Roads and Bridges
The drainage volume of the design manual The objective of drainage design is to provide the
provides general design criteria for necessary roadway drainage facilities which
retention/detention basins as well as procedures allows the public to use the roadway during times
for performing preliminary sizing and final of significant runoff and in a manner that
reservoir routing calculations. The Storage minimizes the potential for adverse effects on
Indication Method is presented as an acceptable adjacent property and existing patterns.
method for detention calculations. Exfiltration
calculations may be required for certain retention The effect of the roadway on the existing drainage
systems for estimations of percolated discharge pattern, the potential flood hazards, as well as the
rates. effect of floods on the roadway are to be assessed
in the design process.
Land-locked drainage areas will require retention
storage areas designed to meet special The engineer shall perform a drainage study in
considerations. accordance with current design methodology,
requirements and criteria in the drainage volume
The collection of field and published data for the
of the design manual. The criteria should identify
planning and location of retention/detention
such items as the hydrology method to be used,
facilities should be coordinated so that it can be
the design storm frequency to be accommodated,
accomplished concurrently with other aspects of a
the allowable spread of water on the pavement to
particular project. A general discussion of data
be tolerated at the specified storm frequency and
collection procedures is presented in Section
any other pertinent hydraulic criteria which is a
311.02.03.
design control for the project. Applicability of
existing Master Drainage Plans will be discussed.
A key element to proper planning of
retention/detention facilities is the selection of
The purpose of the drainage study is to identify
potential sites that will provide control of both
potential drainage problems for the proposed
flooding and stormwater quality. Other important
improvement, to recommend solutions, and to
considerations include:
establish initial pipe and channel sizings and
alignments consistent with the improvement
Runoff quality requirements
concept. The major drainage features shall be
Stormwater management master plan
Part 1 300-20
ROADWAY DESIGN MANUAL Roads and Bridges
displayed on the roadway geometric plans in both The Geotechnical Report will assemble the results
plan and profile. of the subsurface exploration program, analyze,
and make geotechnical engineering
Basic hydrologic conditions should be fully recommendations using the field boring and lab
quantified and discussed. Analysis of test data. This will be presented in an engineering
preconstruction hydrologic conditions should be report, prepared by the engineer for the project
performed in order to evaluate hydraulics and included in the Appendix. The results will be
(capacity, velocity, flood over-topping elevations summarized in the DCR.
etc.) of any existing structures and the impacts of
alternatives considered. The Report is to contain the following
information:
The engineer shall research and evaluate potential
Summary of previous geotechnical
future development (20 year planning horizon)
investigations
within the watershed which may have an impact
description of the program undertaken to
on future drainage flows and ultimately the
identify geotechnical and subsurface elements
performance of existing or proposed hydraulic
which affect project design
structures.
results of surface visual observations
The engineer shall carefully document and groundwater data
photograph all existing drainage problems, a summary of the information obtained from
carefully evaluate recommended solutions and and the location diagram of the soil borings
assure existing conditions are not impacted by the general description of the subsurface
roadway improvements. geologic strata obtained from the soil borings,
including any areas of unacceptable soil
The engineer shall document drainage problems, conditions
design approaches, solutions, and initial hydraulic particle size analysis and potential for scour
structures requirements in a separate Initial results of any material testing
Drainage Study which will be included in the analysis and recommendations for
Appendix. A summary will be presented in the embankment construction including
DCR. settlement and surcharging
an analysis and preliminary recommendations
312 SUBSURFACE for pavement structural section and
INVESTIGATIONS foundations.
Once the project location, horizontal and vertical 313 BRIDGE TYPE SELECTION
alignment and structure requirements have been
generally defined, the engineer will formulate Selection of the most suitable type of structure
subsurface exploration and testing program. The involves investigating alternate superstructure and
objective of the exploration program, is to foundation types including variation of span
provide, specific subsurface information along length, structure depth and number of girders to
successive design sections or reaches of the determine the best bridge type and arrangement
project. The data will allow some basic for a particular site. This is an iterative phase
judgments to be made, i.e., the most suitable where assumptions must be made and later
type(s) of foundations for structures and verified or modified during the process. Detailed
recommended pavement designs to be developed design should not be performed unless it is
during the design phase. necessary to confirm the adequacy of a concept.
In the case of either the structure borings or When performing the concept studies the
roadway borings, the geotechnical program will following shall be considered as a minimum:
serve to reveal the type, severity and extent of
Cost
geotechnical design problems.
Constructability
Maintenance
Part 1 300-21
ROADWAY DESIGN MANUAL Roads and Bridges
For waterway crossings, coordination with the After fully considering the above factors to
project drainage requirements will be necessary. determine the proper structure type, the engineer
The designer should obtain the Initial Drainage will discuss the architectural features with the
Report and thoroughly review the contents before appropriate Municipality Departments. For large
starting the analysis of alternatives. For or controversial projects, approval by the
navigable crossings, the channel width, vertical Executive Council or higher authority will be
clearance, pier protection and navigational aids required. These may be individual or joint
should be investigated and discussed. discussions as dictated by the size, location,
complexity, and sociological, economical,
313.02 WIDENINGS/REHABILITATION ecological and environmental demands of the
project.
On projects involving widenings, in addition to
the requirements for new bridges, the following Through these discussions a structure with
items should be investigated: architectural features that are compatible with
structural, safety and site requirements can be
The existing structure should be checked for developed.
structural adequacy.
The condition of the existing deck joints. The completed Bridge Selection Report shall
The condition of the existing bearings. include a general plan of the bridge. This reduced
The condition of existing diaphragms on steel plan reflects the bridge geometrics, architectural
girder bridges. theme, the bridge substructure and the type of
The existing foundations. foundations. A complete discussion of the cost
Part 1 300-22
ROADWAY DESIGN MANUAL Roads and Bridges
The DCR will include a through discussion of the 316 AGRICULTURE IMPACT
utility impacts and a tabulation of the existing
utility inventory as follows: Agricultural resources are important to mans
survival and therefore must be preserved to the
Item Number greatest extent possible. The Consultant shall
Owner identify the potential impact that the proposed
Description project alternatives may have on these resources
Station within the study area. Primarily, this involves
Part 1 300-23
ROADWAY DESIGN MANUAL Roads and Bridges
determining whether or not the project will 318 SIGNING AND PAVEMENT
directly impact (i.e. irreversibly commit ) land MARKINGS
that is presently used for agricultural purposes.
In the description of impact, the Consultant shall Signing Concept plans will be developed to show
identify whether the land is actively farmed or the major guide signs required for the proposed
fallow as well as the types if crops that would be facility in accordance with the MUTCD and
affected. Impacts will be quantified in hectares. criteria included in Part 2, Section 900, Traffic
Indirect impacts will also be identified and Engineering. It may be necessary to include
described. These may include, but are not limited signing outside of the project limits. New signs or
to, the potential description of the existing modifications required to existing signs shall be
irrigation system or pollution of nearby clearly identified. The signing requirements shall
agricultural lands from untreated stormwater be displayed on a reduced scale version of the
runoff. Impacts associated with each project project geometrics sufficient to show the required
alternative will be compared and the alternative detail. Proposed guide signs should be illustrated
with least agricultural impact shall be identified if graphically with leaders pointing to the sign
such an alternative exists. location. Signing requirements associated with
the construction staging/detour scheme should
317 PUBLIC FEEDBACK also be discussed.
Public involvement is an important aspect in the The signing and lighting concept plans will be
overall success of a project. At the onset of the included in the drawings section of the DCR.
project, the consultant shall develop a Public
Involvement Plan that will establish the approach 319 LIGHTING CONCEPTS
to be used to coordinate project planning and
details with the public. In addition to keeping the This section should begin with a discussion of the
public informed of the project, the plan will also design criteria that governs the location of
provide the public with the opportunity to lighting, the type of lighting relevant to the
comment at various stages of project roadway classification or route and the method of
development. By soliciting and actively illumination analysis. Applicability or
considering public input, the Consultant is more conformance to existing Master Lighting Plans
likely to produce a design that is economically must be considered. Alternative types of lighting
feasible and acceptable to the public. such as high mast at major interchanges should
also be addressed. The typical spacing between
This section of the DCR should briefly describe light sources, and the compatibility with adjacent
the elements of the Public Information Plan, or intersecting lighting system will be shown and
including the location and scheduling of public illustrated on schematic plans.
information meetings, workshops, consensus
building sessions or any other forums aimed at 320 CONSTRUCTION STAGING
soliciting public input. A summary of the
primary issues raised by the public should be
Maintenance of traffic during construction can
presented along with a discussion of how these
have a significant affect on the surrounding traffic
issues have been addressed during the
system, in terms of public convenience, design,
development of the project, and whether or not
cost and the duration of construction. The DCR
consensus has been reached. A file should be
shall include a discussion as to how construction
maintained as backup for each public meeting
of the project will be staged including:
that contains a list of participants and the issues
raised.
Part 1 300-24
ROADWAY DESIGN MANUAL Roads and Bridges
322 CONCLUSIONS/
RECOMMENDATIONS
323 APPENDIX
BILL
BILL DESCRIPTION AMOUNT IN FIGURES
NO.
DH Fs
I GENERAL
II EARTHWORKS
III SUBBASE AND BASE COURSES
IV ASPHALT WORKS
V CONCRETE WORKS
VI SURFACE DRAINAGE SYSTEM
VII WATER WORKS
VIII PRESTRESSED CONCRETE WORKS
IX TRAFFIC MARKINGS AND SIGNS
X SITE LABORATORY
XI CONCRETE PILE FOUNDATIONS
XII METAL WORKS
XIII POST-TENSIONED CONCRETE WORKS
XIV EXPANSION AND FIXED JOINTS
XV IRRIGATION WORKS
XVI LIGHTING AND ELECTRICAL DISTRIBUTION WORKS
XVII TRAFFIC CONTROL SYSTEM
XVIII DAILY WORKS SCHEDULE
XIX TELEPHONE WORKS
XX SEWERAGE WORKS
XXI STREET FURNITURE
XXII PARKING STRUCTURE
XXV LANDSCAPING
Figure 300.02
Cost Estimate Worksheet
Part 1 300-26
ROADWAY DESIGN MANUAL Roads and Bridges
Design speed establishes specific minimum Design speed may be lowered, especially in
roadway design elements. These design elements densely developed urban areas. The design speed
include vertical and horizontal alignment, and for special projects will be established by the
sight distance. Design speed relates indirectly to Road Section. Maximum design speeds, as related
other elements such as pavement and shoulder to roadway classifications, are shown in Table
width, and horizontal clearance. 100.01.
Figure 100.01
Posted Speeds On Abu Dhabi Island
Part 2 100-2
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 100-3
ROADWAY DESIGN MANUAL Roads and Bridges
Mountainous terrain is defined as a roadway The following sections deal with the general
where trucks operate at crawls speeds for long capacity calculations for various roadways. Since
distances or frequent intervals. these calculation methods are lengthy and beyond
the scope of this document, the reader is referred
Table 100.02 to the Highway Capacity Manual (HCM), 1994.
Relation of Conditions to Design Levels of
Service 104.01.01 Multi-lane Rural Roadway
Conditions Design Levels
of Service The general equation for service volume of all
RURAL multi-lane roadways is given by:
Freeway Flat B SV = 2000 N (v/c) T W
Rolling B where:
Mountainous C SV = Service volume (one direction) for a
Expressway Flat B given level of service
Rolling B N = Number of lanes in each direction
Mountainous C v/c = Service volume to capacity ratio
Major Collector T = Adjustment factor for trucks on grades
Flat B W = Adjustment for width and lateral
Rolling B clearance
Mountainous C
Minor Collector (See HCM Section 100.04.02)
Flat C
Rolling C 104.01.02 Two Lane Roadways
Mountainous D
Local Access Flat D Service volumes and capacities for two lane
Rolling D roadways are always both directions without
Mountainous D regard to the distribution of volume by direction.
URBAN
Freeway C The general equation is given by:
Expressway C SV = 2000 (v/c) T W
Arterial (Main Rd) C-D where:
Frontage Road D SV = Service volume in vehicles per hour
Sector Road D (total both directions)
DIRECTIONAL RAMPS B-C v/c = Service volume to capacity ratio
T = Adjustment factor for trucks on grades
W = Adjustment for width and lateral
As an alternative to level of service D,
clearance
consideration should be given to pairs of one-way
roads or alternative bypass routes to improve the
(See HCM Section 100.04.02)
LOS.
Part 2 100-4
ROADWAY DESIGN MANUAL Roads and Bridges
Full Access Control - Gives preference to With the exception of extensive expressway
through traffic by providing access only through frontages, access openings are limited to one
selected frontage/sector roads and by prohibiting opening per parcel. Wherever possible, one
at-grade crossings or direct access from abutting opening should serve two or more parcels. In the
property. case of a large expressway frontage under one
ownership, the feasibility of limiting access to
Partial Access Control - Still gives preference to one opening may be prohibitive, or the property
through traffic but permits some at-grade may be divided by a natural physical barrier such
crossings and some private driveway as a wadi or ridge, making it necessary to
connections. provide an additional opening. However, in the
latter case, it may be preferable to connect the
Approach Road and Driveway Regulations - physically separated portions with a low-cost
Without access control, abutting properties are structure or road rather than permit two
permitted access to the roadway, but the number, openings.
location and geometrics are regulated.
Access rights shall be acquired along interchange
ramps to their junction with the nearest public
road, and shall extend to the end of the ramp taper
Part 2 100-5
ROADWAY DESIGN MANUAL Roads and Bridges
(or at least 50 m beyond the end of the curb provided. See Section 105.03, Use of
return or ramp radius). Frontage Roads, for further discussions.
(8) Access openings on divided roadways shall
In remote areas, infrequent access should be not be permitted within 100 m of a median
accommodated by providing locked gates. This opening unless the access opening is directly
will only be considered for areas that are remote, opposite the median opening.
infrequently used, and have no other access (9) Access approaches shall be limited to right
means. Direct access will not be provided if it turns only unless (1) the approach has no
creates an unsafe condition. Turning movements signalization potential and allowing left turns
will be limited to right turns only. Written would significantly reduce congestion and
approval must be granted by the Abu Dhabi safety problems at a nearby intersection; or
Road Section. (2) there are no intersections, existing or
planned, that allow a U-turn; and (3) left
turns can be safety designed without
105.02.02 Secondary Roadways, signalization.
ADT > 2500 (10)Access approaches with signalization
potential and that require left turn movements
In general, the number of access openings shall be must (1) meet the signalization requirements
held to a minimum for any facility. Additional as specified in Part 2, Section 902,
access may be necessary to satisfy a range of Signalization, and (2) shall not interfere with
design issues/access requirements. The following the location, planning, or operation of the
is a list of issues to consider when providing general road system and nearby property
access points. access.
Part 2 100-6
ROADWAY DESIGN MANUAL Roads and Bridges
between approach roads shall be 5 km for (2) New Alignment. Sector roads generally
these purposes. are not provided on new expressway
alignments since the abutting property
(e) In urban areas with signalized intersections, owners never had legal right of access to
the minimum spacing between access points the new facility. They may be provided,
shall be that which is necessary for the safe however, on the basis of considerations
operation and proper design of intersections mentioned above.
as specified in Section 400.
(3) Existing Alignment. Where an expressway
105.03 USE OF FRONTAGE ROADS is developed parallel to an existing
roadway or local road, all or part of the
(1) General Policy existing roadway is often retained as a
frontage or sector road. Frontage roads
(a) Frontage roads are provided: must be constructed to serve landlocked
To control access to the urban remainders or the remainders must be
expressway and main road purchased outright if other means of
through lanes, thus increasing access cannot be provided. The decision
safety. whether to provide access or purchase
should be based on considerations of cost,
To provide access to sectors. right of way impacts, road system
Maintain continuity of the local continuity and similar factors discussed
road systems. above.
Provide for non-motorized
traffic that might otherwise 105.04 PROTECTION OF ACCESS
desire to use the expressway. RIGHTS
(b) Typically a frontage road is Access Control lines/limits shall be shown on the
justified if their construction costs project right-of-way plans. Where possible, the
are less than the costs of providing right-of-way line and control of access line
other direct access. Right of way should be coincident.
considerations are often the
determining factor. Thus, a For proper control of access, fencing or other
frontage road would be justified if approved barriers shall be installed on all
the investment in construction and controlled access roadways, located on the
extra right of way is less than control or access line where appropriate.
either the severance damages or
the costs of acquiring the affected 106 DESIGN STANDARD
property. Frontage roads may be EXCEPTIONS
required to connect parts of a
severed property or to serve a A design standard exception is a design feature
landlocked parcel resulting from which does not meet the design standards
right of way acquisition. presented in the Roadway Design Manual.
Occasionally these design exceptions are justified
(c) Direct access to the through lanes but it is important that each design exception be
is allowable on expressways. documented and approved in writing prior to plan
However, when the number of acceptance.
access openings on one side of the
expressway exceeds three in 500 The request for approval of design exceptions
m, a frontage road should be shall be in the form of a Design Exception
provided. Request. This request sheet shall be presented to
the Municipality for written approval. The
request sheet shall include the following topics:
Part 2 100-7
ROADWAY DESIGN MANUAL Roads and Bridges
A. Project Description: Briefly describe the C. Provide a thorough brief justification for
project. Note the type of project and/or the design exception. Reasons for
major elements of work to be done, such granting design exceptions include a
as safety or operational improvement, combination of excessive cost, right of
roadway widening, rehabilitation, way impacts and/or environmental
reconstruction, etc. Provide the impacts. Supportive factors have
geographic project limits and length. included low accident frequency, local
opposition, and consistency with adjacent
B. Proposed Project Total Cost: Include a roadway segments.
estimate of the proposed project cost
segregated by major elements, including: 4. ADDITIONAL COST TO COMPLY
roadway, structures, right of way, utility WITH STANDARDS
relocation, environmental mitigation, etc.,
as needed. Provide a realistic estimate of the additional
cost required to meet the design standard for
2. EXISTING ROADWAY which the proposed exception is requested.
Part 2 100-8
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 100-9
ROADWAY DESIGN MANUAL Roads and Bridges
SECTION 200
If providing passing sight distance is not
GEOMETRIC DESIGN
economically feasible, stopping sight distance is
STANDARDS the minimum sight distance provided on multilane
and 2-lane roads. Stopping sight distance is the
201 SIGHT DISTANCE minimum provided for interchanges, at-grade
intersections and private road connections.
201.01 GENERAL
Table 200.01 shows the standards for sight
Sight distance is the continuous length of roadway distance related to design speed.
ahead visible to the driver. There are three distinct
types - passing, stopping, and decision. Passing Table 200.01
sight distance is the minimum sight distance Sight Distance Standards
required by a driver to safely pass another
vehicle. Stopping sight distance is the distance Design Minimum Desired Minimum
required by a driver, traveling at a given speed, to Speed Stopping Stopping Passing
stop after seeing an object on the road. At certain Sight (1) Sight (1) Sight
locations decision sight distance is required to Distance Distance Distance
allow drivers extra time for making decisions. (kph) (m) (m) (m)
30 30 30 220
201.02 PASSING SIGHT DISTANCE
40 45 45 285
50 60 65 345
Passing sight distance is the minimum sight
60 75 85 410
distance required by a driver to safely pass
70 95 115 485
another vehicle. The sight distance available for
80 115 140 545
passing is the longest distance at which a driver
90 135 170 605
whose eyes are 1070 mm above the pavement can
100 160 205 670
see the top of a 1300 mm high object on the road.
110 180 250 730
Passing must be accomplished without reducing
120 205 290 795
the speed of an oncoming vehicle traveling at the
130 235 330 855
design speed. Table 200.01 lists sight distance
standards.
Minimum values shall be avoided in design,
Passing sight distance is only considered on 2- higher values are desirable.
lane roads and should be provided at frequent (1) Increase by 20% on downgrades >3% & >2
intervals. In general, minimum passing sight km. Values shown are for wet pavements.
distance should be provided for 60% of the route
length in level terrain, 40-60% in rolling terrain Chapter III of A Policy on Geometric Design of
and 20-60% in mountainous terrain. Economics Highways and Streets, AASHTO, 1994,
should be weighed against providing passing sight contains a thorough discussion of the derivation
distance or auxiliary passing lanes. of stopping sight distance.
Part 2 200-1
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.01
Stopping Sight Distance on Crest Vertical Curves
Figure 200.02
Stopping Sight Distance on Sag Vertical Curves
Part 2 200-2
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 200-3
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.03
Stopping Sight Distance on Horizontal Curves
If the vehicle is not skidding, all forces are in elements related to speed and horizontal
equilibrium and are governed by the following curvature.
equation:
Table 200.03
Centrifugal Factor = e + f = 0.0079V2 = V2 Maximum Superelevation Rates
R 127R
Roadway emax
Where:
Classification
e = Superelevation rate in m per m
Freeways 0.06
emax = Maximum superelevation rate for
Expressways 0.06
a given condition
Ramps 0.06
f = Side friction factor
Main Roads and Collectors 0.04
R = Curve radius in m
Sector Roads Normal Crown
V = Velocity in kph
Part 2 200-4
ROADWAY DESIGN MANUAL Roads and Bridges
Table 200.04
Values for Design Elements Related to Speed and Horizontal Curvature
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets
Part 2 200-5
ROADWAY DESIGN MANUAL Roads and Bridges
Divided Roadways - The axis of rotation shall be For roadways on the outside of the curve, the
at the median edge of each travelled way. transition will begin/end at the adjust the curve
However, for bridges with decked medians the determined by the inside roadway transition. An
axis of rotation shall be at the centerline. additional transition length is required to rotate
the outside shoulder from -3.0 percent (normal
202.05 SUPERELEVATION shoulder slope) to -1.5 percent (normal pavement
TRANSITION slope). This shoulder transition length must be
added to the pavement transition length to get the
General - Superelevation transition should be total transition length.
designed in accordance with Figure 200.04. The
length of superelevation transition should be Restrictive Areas - In restrictive areas, where
based upon the combination of superelevation rate full superelevation cannot be achieved, the highest
and width of rotation plane. possible superelevation rate and transition length
shall be used. But, in no case shall the cross slope
Edge of travelled way and shoulder profiles rate of change exceed 4% per 20 m.
should be plotted and irregularities and drainage
problems should be eliminated. Superelevation Transitions on Bridges -
Superelevation transitions on bridges should be
Superelevation Transitions - Roadways avoided.
separated by barrier or median will be
superelevated at independent rates. The transition 202.06 SUPERELEVATION OF
length will be based on pavement width and COMPOUND CURVES
superelevation change. The profile of the outside
edge of through pavement cannot differ from the Compound curve superelevation shall be per
profile gradeline by more than the percentage Figure 200.05. Where feasible, the criteria in
shown on Table 200.04 and will be an unbroken Section 202.05 shall apply.
line throughout the transition. The minimum
transition length for a two lane roadway is shown
on Table 200.04. For multiple lane roadways the
minimum length shall increase proportionately.
Part 2 200-6
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.04
Freeway/Expressway Superelevation Transitions
Part 2 200-7
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.05
Superelevation Transitions for Compound Curves
Part 2 200-8
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 200-9
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 200-10
ROADWAY DESIGN MANUAL Roads and Bridges
Flat vertical curves may develop poor drainage in Bridge Deck Drainage - Vertical alignment
the level section. Adjusting the edge grade or design requires special consideration of structure
shortening the vertical curve may be required. drainage. Zero gradients and sag vertical curves
should be avoided on bridges. Parapets collect
Design of these long vertical curves should be large amounts of debris and smaller bridge deck
avoided because many drivers will not pass on drains or scuppers have a higher potential for
curves over 1 km long, despite adequate sight clogging. The minimum desirable longitudinal
distance. It may be more economical to construct slope for bridge deck drainage is 0.2 percent.
passing lanes than to obtain passing sight distance Where vertical curves on bridges cannot be
by using a long vertical curve. avoided, the elevations should be checked to
provide a minimum effective longitudinal grade of
204.05 LONG SUSTAINED GRADES 0.5 percent, and not extend more than 15 m either
side of the sag or crest point.
The maximum grade guideline is not sufficient to
insure uniform roadway operation. The uphill
Part 2 200-11
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.06
Symmetric Parabolic Vertical Curves
Part 2 200-12
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.07
Design Controls for Crest Vertical Curves, for Stopping Sight Distance- Upper Range.
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets
.
Part 2 200-13
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.08
Design Controls for Sag Vertical Curves - Upper Range.
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets.
Part 2 200-14
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.09
Critical Lengths of Grade for Design, Assumed Typical Heavy Truck of 180 kg/kW,
Entering Speed 90 kph.
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets.
Part 2 200-15
ROADWAY DESIGN MANUAL Roads and Bridges
204.07 SEPARATE PROFILE GRADE high approach speeds may result in erratic
LINES operation, especially at night.
For moderate changes in horizontal alignment
Separate grade lines should be considered for all at grade summits, the horizontal curve should
divided roadways. The use of separate grade lines overlap the vertical curve.
provides the opportunity to optimize the vertical Avoid successive changes in profile which are
alignment, drainage features, and provide a safer not associated with horizontal curves. The
more economical design. succession of humps is unattractive.
Horizontal and vertical curvature at
They are not normally considered appropriate intersections should be as flat as physical
where medians are less than 18 m wide. conditions permit.
Exceptions to this may be minor differences Avoid excessive curvature to obtain flat
between opposing grade lines in special grades and tangent alignment or flat curves at
situations. the expense of steep or long grades. It is
better to balance horizontal and vertical
In addition, for either interim or ultimate alignments.
expressways, any appreciable grade differential In general, alignments should be designed to
between roadbeds should be avoided in the take full advantage of scenic opportunities.
vicinity of at-grade intersections. For traffic
entering from the crossroad, confusion and
206 PAVEMENT TRANSITIONS
wrong-way movements could result if the
pavement of the far roadway is obscured because
206.01 GENERAL
of excessive differential.
Figure 200.10
Typical Two-Lane to Four Lane Transitions
Part 2 200-17
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 200-18
ROADWAY DESIGN MANUAL Roads and Bridges
Required for proper drainage. Transitions - A transition from one curb type to
Needed for channelization, delineation, another shall be done in 3.0 m. At curb termini,
control of access, or improving traffic flow the curb should transition from normal curb
and safety. height to zero in 5.0 m.
To protect pedestrians and provide continuity
at ramp connections with local roads. 210 BUS STOPS AND TAXI STOPS
To replace existing curbs.
In urban areas, bus stops and taxi stops will be
To protect the expressway fence on frontage
provided on all main roads.
roads where required.
To prevent ponding in bus and taxi stops on flat
209.02 TYPES AND USES
grades use either a reverse cross slope toward the
main road pavement with slotted trench drains or
Curb types and uses are shown in the current
continue the slope of the roadway and install an
Standard Drawings and are discussed below.
inlet along the loading/unloading curb line.
Precast Curb Type A, B, C - These curbs are
210.01 BUS STOPS
used to deter vehicles from using areas outside the
travelled way, control drainage, and regulate and Bus stops will be located at the far side of
control parking. Type A curbs are typically used intersections and as necessary at midblock
on the outside of the travelled way, adjacent to locations. Near side bus stops should be avoided.
sidewalks and parking lanes. Typical B and C
curbs are used at the median edge adjacent to the Normally, bus stops shall be constructed as
green area. shown on the current Standard Drawings. Under
restrictive conditions these standards may be
The above curb types are classified as barrier reduced to 15.0 m length, 10.0 m tapers and 3.25
curbs and are not generally used on high-speed m width.
roadways as they present a safety hazard for
errant vehicles. A continuous concrete barrier At all bus stops a 4.0 m wide sidewalk shall be
(safety shape) should be used where it is provided along the loading/unloading area. This
necessary to control drainage or access on high- shall be connected to the nearest sidewalk with a
speed roadways. 4.0 m wide perpendicular sidewalk.
Part 2 200-19
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 200-20
ROADWAY DESIGN MANUAL Roads and Bridges
parking stalls are similar to those given on the 3. determine the need for added parking facilities
Standard Drawings. and establish an approximate location for
such parking.
Parallel parking stalls should have a length of 7.0
m and a desirable minimum width of 2.5 m as The required analysis regarding parking will thus
shown on the Standard Drawings. vary from project to project since parking demand
is sensitive to site-specific factors, such as land
Where sector roads are widened to provide use and proposed community developments.
parking stalls, the widened sector road
arrangement should not be carried through sector In the absence of site specific parking criteria,
road/sector road intersections. The fillets at such Table 200.09 should be used. Also refer to Part 1,
intersections (usually 5.0 m radii) should be Section 202.02.11 for further parking
positioned to line up with the edge of the travelled requirements.
lanes.
Table 200.09
211.04 PARKING LOTS Parking Requirements
Part 2 200-21
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.11
Typical Parking Facilities
Part 2 200-22
ROADWAY DESIGN MANUAL Roads and Bridges
Travelled way width is one of the most important Table 300.01 summarizes the minimum
safety factors in design. A wide two-lane two-way continuous usable width of paved shoulder for
pavements provides higher capacity, higher driver various roadway classifications.
comfort levels, consistent operation and lower
accident rates. Table 300.01
Paved Shoulder Width Standards
Minimum travelled way widths of 7.30 m shall be
provided on all design classes of roadways. Roadway Inside Outside
Class Shoulder Shoulder
Traffic lane widths shall be 3.65 m, and the
/ verge / verge
number of lanes required shall be based on the
(m) (m)
projected traffic volume and roadway
RURAL
classifications. Loop ramp lanes shall be 5.0 m.
Freeway 3.0 4.0/2.0
Expressway 3.0 4.0/2.0
See Section 302 for general shoulder widths and
Collector - 2.4
see Section 305 for specific roadway cross
Local Access 2.0
section widths.
URBAN
Freeway 3.0 4.0/2.0
301.02 TRAVELLED WAY CROSS
Expressway 3.0 4.0/2.0
SLOPES
Arterial (Main Rd) - 4.0/2.0
Frontage Road 1.2 1.2
Tangent cross slope is balanced between steep
Sector Road - -
cross slopes, desirable for drainage and the fact
2-LANE RAMP 2.4/2.0 3.0/2.0
that vehicles drift toward the lower pavement
LOOP RAMP 2.0/1.0 3.0/1.0
edge on steep cross slopes. Generally, cross
slopes below 1.5 percent have little effect on The verge is the area outside the paved shoulder,
vehicle steering. Cross slope values for the usually rounded, at the top of embankment
various roadway classifications are provided in slopes.
the following sections.
302.02 SHOULDER CROSS SLOPES
Unpaved travelled ways shall have a cross slope
of 3.0 percent.
In normal tangent sections, inside shoulder slope
shall match the travel lanes and outside shoulders
See Section 305 for specific roadway cross slope
shall slope on a 3% grade away from the travelled
rates.
way.
Pavement superelevation on curves shall be as
determined in Section 202.
303 SIDE SLOPE STANDARDS
should be rounded 3.0 m where the material is Shoulders - Shoulder widths for various roadway
other than solid rock. classifications are summarized in Table 300.01.
Unpaved, landscaped medians between curbs On structures, the cross-slope shall be 1.5 percent
shall be graded flat. Other unpaved medians uniformly across the inside shoulder, driving
should slope downward from the shoulders to lanes, and outside shoulder.
form a shallow valley. Cross slopes should be
1:10 or flatter 1:20 being preferred. Slopes as Profile Grade Line - The profile grade line shall
steep as 1:6 are acceptable if necessary for be at the median edge of the travelled roadway.
drainage.
305.02 URBAN FREEWAY/
See Section 305 for specific roadway median EXPRESSWAY CROSS
requirements. SECTION
305 CROSS SECTION ELEMENTS General - The typical section for urban
expressways shall be comprised of two roadways,
See Figure 300.01 for typical cross sections of with shoulders, divided by a median. Due to space
various roadway classifications. limitations, the cross section may vary. The final
configuration shall be determined during the
Pavement Structure - For the Standard concept phase of design.
Pavement Structures, see current Standard
Drawings. Also, refer to Section 604 Structural
Pavement Section Design.
Part 2 300-2
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.01
Typical Cross Sections
Part 2 300-3
ROADWAY DESIGN MANUAL Roads and Bridges
Travelled Roadways - Each roadway will Parking, Loading/Unloading Lanes - Except for
consist of a minimum of three 3.65 m wide taxi stops and bus stops, no parking or
through lanes. Ramps shall be one 5.0 m lane, loading/unloading spaces shall be provided on
and where volumes demand, two 3.65 m lanes. main roads without being separated from the
traffic lanes by a wide curb.
Median - A minimum 7.0 m wide median shall be
used. However, a 10.0 m median width is Median - A median with 22 cm high curbs shall
desirable. The median may be either unpaved and be provided. The median width should be at least
depressed (if 20.0 m wide or more), or it may 5.0 m. Where an existing street with a median of
have concrete barriers. less than 5.0 m is being upgraded, the median
should be increased to 5.0 m if possible. Where
Cross Slope - Except in superelevated sections, a an existing street with a median width of greater
uniform cross slope of 1.5 percent shall be than 5.0 m is being upgraded, the existing median
applied across the inside shoulder and driving width should be maintained for planting. Median
lanes. The outside shoulder will have a cross width shall be reduced to permit exclusive left-
slope of 3.0 percent. The pavement will slope turn lanes at intersections where required.
toward the outside of the section.
No provision shall be made for U-turns except at
On structures, the cross slope shall be 1.5 percent intersections.
uniformly across the inside shoulder, driving
lanes, and outside shoulder. Curbs - Curbs shall be provided along all edges
of pavement in urban areas. Curb types and uses
Profile Grade Line - The profile grade line shall are shown in the current Standard Drawings.
be the median edge of the travelled roadway.
Sidewalks - Sidewalk widths and locations will
305.03 ARTERIAL (MAIN ROAD) vary but the minimum width shall be 2.0 m and
CROSS SECTION they shall be located to provide pedestrian
movement continuity. In addition, whenever
The standard cross section of roadways is possible a 2.0 m wide sidewalk adjacent to the
comprised of two unidirectional pavements, pavement and green areas should be provided
median, sidewalks, service reservations and green primarily for aesthetic purposes.
areas.
Pedestrian crosswalk ramps shall be used at all
Pavement and Lane Widths - The pavement will intersections and all other locations where the
consist of a minimum of three traffic lanes in each main pedestrian sidewalk crosses curb lines.
direction divided by a raised median. Wherever
necessary, auxiliary lanes shall be provided for Cross Slope - All pavement will have a broken
turning movements. Auxiliary lanes, whether cross-slope of 1.25 percent sloping away from the
allocated to through traffic or to turning median across the two inside lanes and 2.0
movements, shall be 3.65 m wide. percent for the outside lanes. A 1.5 percent cross-
slope shall be provided toward the pavement on
Free Right Turn Islands and Lanes - Exclusive sidewalks. Cross-slope will vary at intersections
right-turn lanes and islands shall be used in accordance with current Standard Drawings.
wherever possible. No more than one exclusive
right-turn lane shall be provided in any direction. Profile Grade Line - The profile grade line shall
be the median edge of pavement.
Left Turn Lanes - Unless otherwise approved by
the Municipality Road Section under special
conditions, no more than one left-turn lane shall
be provided from the median.
Part 2 300-4
ROADWAY DESIGN MANUAL Roads and Bridges
The cross section for sector roads will consist of Pavement and Lane Widths - The minimum
an undivided two-directional roadway. Curbs paved cross section for urban frontage roads shall
shall be provided along both edges of pavement. be two 3.65 m lanes with curbing. The minimum
paved cross section for rural frontage roads shall
Pavement and Lane Widths - Lane width shall be 3.65 m lanes with 1.2 m paved shoulders.
be 3.65 m for two lanes in each direction and 4.0
to 5.0 m for one lane in each direction. Cross Slope - All pavement will have a 1.5
percent uniform cross slope either at a straight
Free Right Turn Islands and Lanes - No free cross slope from one edge of pavement to the
right turn islands or lanes shall be used in the other or by utilizing a crowned roadway design.
design of sector roads.
Outer Separation - Outer separation is the
Left Turn Lanes - Left turn lanes shall not be distance from the main road travelled way to the
used in the design of sector roads. frontage road travelled way. In urban and
mountainous areas, the outer separation should be
Parking Loading/Unloading Lanes - Generally, 8.0 m minimum. In rural areas, other than
no loading or unloading lanes shall be provided on mountainous terrain, the outer separation should
Sector Roads. It is up to the designer and Design 12.0 m minimum.
Project Manager to determine the need and type
of on-street sector road parking. If required, see Headlight Glare - Frontage road design shall
Section 211, Parking. account for potential headlight glare interfering
with the vision of oncoming motorists. The
Median - Sector roads shall not have medians. preferred measures to prevent headlight glare
interference on new construction are wider outer
Curbs - Curbs shall be provided along the outside separations, revised alignment and raised or
edge of sector roads. Types and uses are shown in lowered profiles.
the current Standard Drawings.
306 HORIZONTAL AND VERTICAL
Sidewalks - Sidewalk widths and locations will CLEARANCES
vary but minimum width shall be 2.0 m.
Whenever possible a 2.0 m wide sidewalk 306.01 HORIZONTAL CLEARANCES
dividing the pavement and green areas should be
provided. The sidewalk surface will slope toward Unshielded Horizontal Clearance - The
the roadway at a uniform cross slope of 1.0 minimum desired horizontal clearance between the
percent. travelled way edge and fixed objects shall be the
clear zone width. Fixed objects within the clear
Pedestrian crosswalk ramps shall be used at all zone shall be eliminated, moved, redesigned
intersections and all other locations where main (breakaway design), or shielded (see barrier
pedestrian traffic crosses curb lines. design below ) where practical.
Cross Slope - All pavement will have a 1.5 Shielded Horizontal Clearance - If fixed objects
percent uniform cross slope either at a straight cannot be eliminated, moved or redesigned then
cross slope from one edge of pavement to the lesser clearance is allowable if barriers or
other or by utilizing a crowned roadway design. guardrail is used to shield the object.
Sector roads shall not have superelevation.
The clearance to fixed objects such as bridge
Profile Grade Line - The profile grade line for rails, concrete barriers, abutments, retaining
sector roads shall be the centerline or as walls or noise barriers on all roadway facilities,
determined by the Consultant. shall be equal to the standard roadway shoulder
Part 2 300-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 300-6
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.02
Clear Zone Distance Curves
Part 2 300-7
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.03
Horizontal Curve Adjustments Factors
Part 2 300-8
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.04
Clear Runout Area
Part 2 300-9
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.05
Preferred Vee-Ditch Cross Sections
Figure 300.06
Preferred Trapezoidal ditch Cross Sections
Part 2 300-10
ROADWAY DESIGN MANUAL Roads and Bridges
As previously stated, if hazards exist within the Roadside barriers are also designed with varying
borders of the clear zone, efforts shall be made to heights to counteract overturning moments of
eliminate the hazard first, prior to considering trucks with high centers of gravity. The basic
barrier installation. These considerations can roadside barrier is designed at 810 mm high. At
include any of the following: this height, the roadside barrier can successfully
Regrading of roadside topography in the clear redirect 820-2000 kg vehicles, and occasionally
zone to a smooth and safe cross section. redirect 18,000 kg buses at moderate impact. A
Extend exposed pipes, culverts and install roadside barrier designed at 1070 mm high, have
headwalls outside the clear zone. successfully redirected a 36,300 kg tractor-trailer
with impact conditions of 15 at 84 kph.
Part 2 300-11
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.07
Risk Warrants for Embankments
Part 2 300-12
ROADWAY DESIGN MANUAL Roads and Bridges
308.03.03 Effects of Roadside Terrain Runout Lengths (LR) and Hazard Lateral
Distance (LH) - When designing the length of a
The profile between the edge of traveled way and barrier, the two primary factors that must be
the barrier can have significant effects on the final considered are:
placement of the barrier. The vehicles wheels
should remain in contact with the ground and its LR - Runout Length
suspension system neither compressed or LH - Hazard Lateral Distance
suspended at the moment of impact with the
barrier. This holds true for all barrier systems. The runout length (LR) is the distance a vehicle
Locations of roadside curbs and slopes require needs to stop prior to colliding with a hazard once
particular attention when determining barrier it has left the roadway. Its distance is measured
design and placement. from the point the vehicle is assumed to leave the
roadway to the hazard ahead. Runout length
Curbs - Guardrail/Curb combinations are highly requirements vary according to the roadway
discouraged in locations where high-speed and design speed. See Figure 300.04.
high angle impacts are likely to occur. Areas
with no alternative but to use this combination The lateral distance (LH) is the distance between
shall use a curb less than 100 mm or, stiffen the the edge of the travelled way to the far side of the
guardrail to reduce deflection by bolting a w- hazard, if the hazard is a fixed object. If the
beam to the back of the posts or by adding a rub hazard is an embankment, the lateral distance
rail. would be extended to the edge of the clear zone.
If the hazard extends beyond the clear zone, the
Slopes - As previously mentioned, guardrail minimum lateral distance would be only to the
performance is affected by the vehicles position edge of the clear zone.
at moment of impact. Crash tests show, roadside
barriers perform most effectively when installed After determining the runout length and lateral
on slopes 1:10 or flatter. distance, the length of the barrier depends on the
barrier tangent length, barrier lateral offset, and
308.03.04 Barrier Length Design flare rate.
Figure 300.08
Roadside Barrier Types and Features
Part 2 300-13
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.09
Barrier Layout Diagram
Part 2 300-14
ROADWAY DESIGN MANUAL Roads and Bridges
Barrier Tangent Length (LT) and Barrier Median barriers are warranted in locations that
Lateral Offset (L1) - The barrier tangent length have a history of cross-median accidents. On
(LT) is the portion immediately ahead from the roadways that have wide medians, (greater than
hazard and parallel to the roadway. It is of nine meters) median barriers generally are not
variable length, selected by the designer, and warranted unless there is a history of cross-
shall be at least as long as the flared section of the median accidents or there are fixed object hazards
barrier. within the median.
The barriers lateral offset (L1) is the distance 308.04.02 Median Barrier Types and
between the edge of travelled way to the barrier. Features
This offset is also selected by the designer and
shall be as far away from the edge of travelled There are three types of commonly used median
way as possible. This provides an unobstructed barriers. See Figure 300.10.
recovery area to allow an out of control vehicle to
gain control without colliding with the barrier. Concrete Safety Shape Median Barrier
Single Face Concrete Barrier
Flare Rate (b:a) - The flared portion of the Metal-Beam Guardrail
barrier is not parallel to the roadway. Flared
sections are used mainly to introduce the barrier The concrete safety shape barrier is the most
toward the barrier line or a narrower segment of commonly used median barrier, and shall be
the roadway. The flared transition decreases the installed in most locations requiring a barrier. In
likelihood that the barrier is perceived as a hazard areas where the adjoining sections of roadway
by motorists. have previously installed a Metal Beam Guardrail
consideration may be given to continue using it
Flared barrier sections have their disadvantages. for that segment. Single face Concrete Barriers
The greater the flare rate, the greater the angle of are used mainly to shield hazards or for earth
impact from an approaching vehicle. This may berm support.
increase the magnitude of injuries particularly
with rigid barriers. Barrier flares can also 308.05 MEDIAN BARRIER
increase the probability that an impacting vehicle PLACEMENT
will be redirected across the roadway and into
incoming traffic. This is particularly dangerous if The two primary factors to consider when placing
the roadway has two-way traffic not separated by median barriers are:
a median or a median barrier. Therefore, flatter
flare rates shall be used particularly in locations Median Geometry
with two-way traffic or steep embankments. Treatment of Fixed Object Hazards in the
Median
See Figure 300.09 for barrier layout diagram.
308.05.01 Median Geometry
308.04 MEDIAN BARRIERS
As previously mentioned, a median that is flat
308.04.01 Median Barrier Warrants (1:10 or flatter), relatively smooth and clear of
fixed obstacles is desirable. If a median barrier is
A Median barriers primary function is to warranted under these conditions, it shall be
separate opposing traffic on a divided roadway installed at the center of the median.
and/or shield fixed object hazards within the
median. Like all types of barriers, median If the median is a v-shaped foreslope embankment
barriers shall only be installed if it is less or a ditch and warrants a barrier, it shall be
hazardous colliding with the barrier than not installed near the shoulder on both sides of the
having a barrier installed at all. Barrier median.
installation shall be considered only if the fixed
object hazards can not be removed.
Part 2 300-15
ROADWAY DESIGN MANUAL Roads and Bridges
If the full width of the median is a foreslope 308.05.02 Treatment of Fixed Object
embankment steeper than 1:10, and warrants a Hazards
barrier, the barrier shall be installed on the higher
edge of the median. If the slope is 1:10 or flatter In some situations, the entire median does not
and requires a barrier, the barrier shall be require a barrier system. However, there may be
installed at the center of the median. However, if hazards in the median that require shielding.
the median is rough cut, obstructed with hazards, Treatment of hazards can include but not limited
and non-traversable, barriers shall be installed, at to those illustrated in Figure 300.11.
the edge of both shoulders.
308.06 END TREATMENTS AND
If the median is a backslope that is rough cut, CRASH CUSHIONS
non-traversable or is inside the clear zone area,
barriers shall be installed on both sides of the 308.06.01 End Treatments
median to avoid vehicle snagging. If the
backslope is traversable but sufficiently steep to All roadside and median barriers terminating
redirect vehicles, a semi rigid barrier can be within the clear zone and/or are located where
installed on the high point of the slope. they have a high probability of being hit head-on,
shall terminate with a crashworthy terminal on the
approach end of the barrier. Refer to the most
recent edition of the AASHTO Roadside Design
Guide.
Figure 300.10
Median Barrier Types and Features
Part 2 300-16
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 300.11
Treatment of Fixed Hazards
Part 2 300-17
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 300-18
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 400.01
Basic Intersection Types
Part 2 400-1
ROADWAY DESIGN MANUAL Roads and Bridges
intersecting legs, topography, traffic patterns, and Give preference to major traffic movements.
desired operation. Intersections within a basic Reduce areas of conflict.
type vary greatly however, the general application Cross traffic at right angles (75-90o desirable
of at-grade intersection design is common to all. - skew no more than 60o.)
Traffic volume, design speed, and the roadway Separate points of conflict.
classification are the principal factors used to Provide speed-change lanes and separate
determine intersection type. turning lanes where appropriate.
Restrict undesirable movements.
Three-Leg Intersection - The three-leg Provide adequate width to shadow turning
intersection has three intersecting legs which form traffic.
a T or a Y. Operationally three-leg and four- Enhance signal control.
leg intersections are preferred and multidirectional
"Y" intersections and intersections with more than
404.01 PREFERENCE TO MAJOR
four legs should be avoided.
MOVEMENTS
Four Leg Intersections - Four-leg intersections Whenever possible, preference should be given to
may be right angled, oblique, or offset. The right- the major traffic movements. This usually requires
angled crossing is easily signed and signalized, stopping, funneling, or eliminating minor
provides good visibility, and is the safest to movements. Controlling measures should conform
negotiate. The oblique crossing creates problems to natural movement paths and be introduced
with visibility, pedestrian safety, and vehicle- gradually to promote smooth and efficient
turning angles. The offset intersection has low operation.
capacity, is difficult to comprehend and negotiate,
and is difficult to sign and signalize. 404.02 AREAS OF CONFLICT
Multileg Intersections - These intersections have Large multilane undivided intersection areas are
more than four legs and can have several undesirable because drivers cannot predict the
configurations. Multileg intersections are other vehicles movements. By separating traffic
confusing, have poor visibility, poor turning movements into definite travel paths
angles, and are difficult to sign, mark, and channelization reduces these conflicts.
signalize. This type of intersection should be Channelization also separates points of conflict
avoided if possible. within the intersection and clearly defines vehicle
pathways.
Roundabout Intersections - Roundabout designs
generally have three or four legs joining a circular 404.03 INTERSECTION ANGLES
roadway. All traffic turns right to merge with
traffic in the roundabout. Traffic continues to A 90o intersection provides the shortest crossing
turn right through the circle to eliminate through for intersecting traffic and provides the most
and left turn movements. Roundabout designs are favorable condition for drivers to judge the
characterized by light traffic volumes and slow relative position and speed of approaching
speeds through the intersection. The roundabout vehicles. The minimum desirable intersection
intersection is a design that can be used in lieu of angle is 75 degrees. Intersection angles less than
the traditional three or four leg intersections. For 60 degrees should be realigned.
further descriptions and types see Part 2, Section
407, Roundabout Design. 404.04 POINTS OF CONFLICT
Part 2 400-2
ROADWAY DESIGN MANUAL Roads and Bridges
Properly sized traffic islands can provide refuge Avoid complex intersections that present
for vehicles and pedestrians. The shadowing multiple movement options or decisions.
effect of islands provides refuge for vehicles
waiting to cross or enter an uncontrolled traffic Accident records provide a valuable guide to
stream. the type of channelization needed.
Channelization can also provide a safer crossing The Standard Drawings include details for a
of two or more traffic streams by permitting channelized free right turn and typical
drivers to select adequate gaps in one traffic pavement markings at intersections.
stream at a time. Channelization should also
provide ample storage for vehicles to make the
turning or crossing movements.
Part 2 400-3
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 400-4
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 400-5
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 400.02
Design Vehicle Dimensions
Part 2 400-6
ROADWAY DESIGN MANUAL Roads and Bridges
This turning template shows the turning paths of the specified AASHTO design vehicle. The paths shown
are for the left front overhang and the outside rear wheel. The left front wheel follows the circular curve,
however, its path is not shown.
Figure 400.03
Minimum Turning Path for P Design Vehicles
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets
Part 2 400-7
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 400.04
Intersection Sight Triangles
Part 2 400-8
ROADWAY DESIGN MANUAL Roads and Bridges
d = 0.28V(2.0+ta)
S = D+W+L
Figure 400.05
where: D = distance from near edge-of- Sight Distance at Intersections Acceleration
travelled way to the front of a from Stop.
stopped vehicle (typically 3.0 From AASHTO, 1004, A Policy on Geometric
m). Design of Highways and Streets
W = travelled way width along path
of crossing vehicle (m)
L = overall length of vehicle (m)
Part 2 400-9
ROADWAY DESIGN MANUAL Roads and Bridges
Turning Left Onto a Major Roadway - requirement for the right-turn maneuver is
Because it takes longer to turn and accelerate to approximately one meter less than that required
operating speed than to go straight across an for the left-turn maneuver in Turning Left Onto
intersecting roadway, the critical sight distances a Major Roadway. See Figure 400.07 curve Cb
are those required for turning movements. The for the required sight distance for a vehicle
driver must have sufficient sight distance to the turning right and accelerating to 85 percent of the
left to cross the near lanes(s) without interfering design speed before being overtaken by vehicles
with oncoming traffic. The driver must also have slowing to 85 percent of design speed. Trucks
sufficient sight distance to the right to turn left will take considerably longer than passenger
and accelerate to a speed where oncoming traffic vehicles.
is not significantly impaired.
Signal Control - Because of unanticipated
The sight distance required to the left are vehicle conflicts at signalized intersections, (such
calculated from: as, signal violations, right-turns on red, signal
malfunction, or use of flashing red/yellow mode)
dL = 0.28V(2.0+ta) the requirements for Stop Controlled
intersections should be met. At intersections
where: dL = sight distance required to the where right-turns on red are permitted, the
left along the major roadway departure sight line for right-turning vehicles
from the intersection (m). should be determined by the methods for
V = design speed on the major Turning Right into a Major Roadway."
roadway (kph)
ta = time required to accelerate and Stopped Vehicle Turning Left from a Major
traverse the distance to clear Roadway - The driver will need sufficient sight
the traffic in the lane distance ahead to turn left and clear the opposing
approaching from the left. travel lane(s) before an approaching vehicle
reaches the intersection. The sight distance
The required sight distance to the right is based required is calculated from:
on the assumption that the mainline vehicle will
slow to 85 percent of the design speed and d = 0.28V(2.0+ta)
maintain a 2.0 second gap from the turning
vehicle. To calculate the necessary sight distance where: d = sight distance required along
first determine from Figure 400.06 the distance P the major roadway from the
required for the turning vehicle to reach a speed intersection (m).
of 85 percent of the mainline design speed. The V = design speed on the major
sight distance required to the right is calculated roadway (kph)
from: ta = time required to accelerate and
traverse the distance to clear
dR = (t+2)(.28)(.95V) - (P-5- the traffic in the approaching
(.56)(.85V) - Lv) lane.
where: dR = Sight distance required to 406.02 EFFECT OF SKEW
the right along the major
roadway from the Intersection skew has no effect on sight distance
intersection (m). requirements since they are measured along the
T = time required to travel intersecting legs. However, the sight triangle
distance P (Table 400.01). configuration is affected by skew. Care should be
V = mainline design speed taken to verify that the area within the sight
(kph) triangles can be constructed and maintained to
Lv = Vehicle Length (m) provide a unobstructed view throughout the sight
triangle with a 1070 mm eye height on the minor
Turning Right Onto a Major Roadway - The road to a 1300 mm object height on the major
right-turning-vehicle must have sufficient sight road.
distance to the left to complete its turn and
accelerate to a predetermined speed before being Skew also affects the distance a vehicle travels to
overtaken by approaching traffic travelling at the cross the intersection. Heavily skewed
same predetermined speed. The sight distance intersections should be controlled.
Part 2 400-10
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 400.06
Acceleration Curves
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets
Part 2 400-11
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 400.07
Intersection Sight Distances
For turning onto a major roadway AASHTO, 1994,
A Policy on Geometric Design of Highways and Streets
Part 2 400-12
ROADWAY DESIGN MANUAL Roads and Bridges
406.03 EFFECT OF VERTICAL be 3.65 m. Three meter wide left-turn lanes may
PROFILES be used on low speed urban roadways. The width
is measured from the adjacent edge of travelled
A vehicle descending a grade requires greater way, excluding shy distance.
stopping distance than one on level ground.
Conversely, a vehicle ascending a grade requires Medians - To improve left-turn visibility, the left-
less distance to stop. Grades up to 3 percent have turn-lane should be placed as far to the left as
little effect on stopping sight distances. In no case possible in the median leaving only the painted or
should the grades exceed 6 percent. curbed nose. Excess width between the left-turn
lane and the adjacent same-direction through lane
For Stop Controlled intersections, the time should be treated as painted island. When left-
required to cross a roadway is affected by the turn lanes are placed in raised (curbed) medians,
crossing grade. If the grade is significant, the a minimum nose width of 1.0 m should remain for
sight distance should be increased. pedestrian refuge and traffic control devices.
Where the intersection leg grades are other than Approach Tapers - On roadways with narrow or
flat, corrections should be made to the sight no medians, room for the left-turn lane is made by
distances using the approximate ratios given in shifting traffic laterally to the right. The taper
Table 400.02. length used to effect this shift should be 0.6WV,
where W = lateral shift (m) and V = design speed
Table 400.02 (kph).
ta Adjustment For Grade
Sight Triangle Distances Bay Tapers - The bay taper length should be
Ratio, ta on grade / ta level (Figure 400.05) short to clearly identify the additional lane.
Generally the taper length should be 15:1.
Crossroad Grade %
Deceleration Length - Whenever feasible, the
Design Vehicle -4 -2 0 2 4 left-turn lane should provide deceleration clear of
P 0.7 0.9 1.0 1.1 1.3 the through lanes. The minimum deceleration
SU 0.8 0.9 1.0 1.1 1.3 lengths, exclusive of bay taper and vehicle
WB-15 0.8 0.9 1.0 1.2 1.7 storage, for 50, 60 and 80 kph are 70, 100 and
130 m, respectively.
Use this table to adjust ta values for effect of
grade. Based on the likely range of crossing In urban areas, it may not be possible to provide
distances. the deceleration lengths and maintain the storage
and approach taper lengths required. In these
situations, these lengths should be used as a
406.04 LEFT-TURN
desirable goal.
CHANNELIZATION
General - A left-turn lane expedites through Storage Length - The storage length should be
sufficient:
traffic flow, controls turning traffic movement,
and improves the intersection safety and capacity.
To store the number of vehicles during
The left-turn lane should be laid out such that the critical periods.
turning vehicle must make a definite move to To avoid left-turning vehicles stopping in the
enter the lane. The desirable length of the left-turn through lanes.
lane is the sum of the required storage length and So the lane entrance is not blocked by
deceleration length, including the bay taper standing through traffic.
length.
Refer to the Highway Capacity Manual, Special
Width - The desirable left-turn lane width should Report No. 209, Transportation Research
Board, 1986 for further discussion.
Part 2 400-13
ROADWAY DESIGN MANUAL Roads and Bridges
General - Right-turn lanes improve intersection Free Right-Turns - Uncontrolled free right-
capacity and safety. As for left-turn lanes, right- turns improve capacity of an intersection with a
turn lanes should be laid out such that a right- heavy right-turn demand. The right-turn is made
turning vehicle must make a definite move to "free" by channelizing the turning movement
enter the lane. outside of the intersection controls. Free right-
turns shall only be provided where the turning
The desirable length of the right-turn lane is the movement can be made into an auxiliary or
sum of storage requirements and deceleration acceleration lane.
length, including bay taper.
406.06 TRAFFIC ISLANDS
Width - The desirable right-turn lane width
should be 3.65 m. Three meter wide right-turn General - Traffic islands are located between
lanes may be used on low speed urban roadways. traffic lanes and are commonly designated using
The width is measured from the adjacent edge of paint, raised pavement markers, or curbs. They
travelled way, excluding shy distance. serve to:
The normal shoulder should be provided at the confine specific traffic movements into
right-turn lane although, if right of way is definite channels;
severely constrained, a minimum 1.2 m wide separate traffic moving in the same or
shoulder may be used. The normal curb should be opposite direction;
carried through the right-turn section. aid and protect pedestrians crossing the
intersection; and,
Approach Tapers - Generally right-turn lane discourage or prohibit undesirable
approach tapers are not required because the lane movements.
is added to the outside of the travelled way and
the travel lanes are not shifted. However, if the Design - Traffic islands must be large enough to
travel lanes must be shifted to accommodate a be seen and to command the attention of the
right-turn lane, the taper should be the same as driver. Islands for channelizing should preferably
for left-turn lanes. be at least 9.0 m2. Curbed islands for separating
traffic streams should not be less than 1.0 m wide
Bay Tapers - The bay taper which guides the and 8.0 m long.
motorist into the right-turn lane is a straight line
along the right edge of the travelled way. Curbed islands should be offset from the through
Generally the taper length should be 15:1. traffic lanes by a minimum shy distance of 0.6 m
and 0.9 m is preferable for approach speeds
Deceleration Length - Whenever feasible, the greater than 25 kph.
right-turn lane should provide deceleration clear
of the through lanes. The minimum deceleration The approach end of a curbed island should be
lengths, exclusive of bay taper and vehicle rounded at 0.5 to 1.0 m radius and tapered at 15:1
storage, for 50, 60 and 80 kph are 70, 100 and to guide the driver into the channelization.
130 m, respectively.
Where there is an approach shoulder (1.2 m or
In urban areas, it may not be possible to provide wider), the curbed island should be offset from
the deceleration lengths and maintain the storage the through lane by the width of the shoulder.
and approach taper lengths required. In these With an approach shoulder the flared approach is
situations, these lengths should be used as a not necessary, except where a deceleration or
desirable goal. turning lane has been provided.
Part 2 400-14
ROADWAY DESIGN MANUAL Roads and Bridges
Avoid curbed traffic islands where the approach roundabout. For these reasons roundabouts
operating speeds are 80 kph or greater. tend to be removed and replaced with
Mountable curbs should be used at curbed islands conventional signalized intersections instead
except where barrier curbs are provided for of being modified.
greater pedestrian protection. Roundabouts require more land than
conventional intersections.
407 ROUNDABOUT DESIGN Roundabouts are not well suited for
pedestrian traffic, because pedestrians are not
There are three main types of roundabouts, able to walk in a clear path through the
Normal, Mini and Double. There are other forms intersection. In areas of high pedestrian
of roundabouts but they variations of these basic traffic, pedestrians can cause major problems
types. They are Ring Junctions, Grade Separated with illegal crossings.
and Signalized Roundabouts. More information
about the use and design of these and other Normal Roundabouts: The normal
roundabouts can be found in the Geometric configuration of a roundabout is made up of a
Design of Roundabouts. When reading this one-way road around a circular curbed island 4m
design manual the designer should be aware that or more in diameter. The approaches are usually
the manual was written for left-hand running flared to allow multiple vehicle entries. The
traffic and appropriate modifications should be number of entries should be limited to three or
made for when adapting these standards to right- four arms. The efficiency and driver
hand running traffic patterns. comprehension decreases as the number of arms
is increased. The minimum radius of curvature
The roundabout is used at intersecting streets with also increases with additional arms which can
low capacity and low design speed. Roundabouts raise circulatory speeds. Double roundabouts can
should be considered when they are cost effective be an alternative under these conditions. See
or increase safety over standard intersection Figure 400.08.
designs.
Part 2 400-16
ROADWAY DESIGN MANUAL Roads and Bridges
SECTION 500
INTERCHANGES 503 DESIGN CONSIDERATIONS
Part 2 500-1
ROADWAY DESIGN MANUAL Roads and Bridges
Figure -500.01
Three-Leg Interchanges
From AASHTO, 1994," A Policy on Geometric Design of Highways and Streets".
Part 2 500-2
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 500.02
Simple Diamond
Advantages -
High design standard single exits in advance
Figure 500.03
of the structure.
Single Point Diamond Interchange
High design standard single entrances
beyond the structure.
Requires relatively little right-of-way.
Part 2 500-3
ROADWAY DESIGN MANUAL Roads and Bridges
Advantages
Relatively narrow right-of-way.
Opposing left turns pass to the left of each
other.
Traffic signal is three-phase rather than four.
Operates with a single traffic signal reducing
delay through the ramp intersection.
Handles high volume left-turns on the cross
road more efficiently than a diamond.
Curve radii for left-turn movements through
the intersection are significantly flatter than
at conventional intersections, and therefore
the left turns move at higher speeds.
Higher capacity than a conventional tight
diamond interchange.
Figure 500.04
Disadvantages - Cloverleaf
Higher construction cost than a conventional
tight diamond interchange.
Extensive retaining walls required where Advantages -
right-of-way is restricted. Left-turn conflicts eliminated
Vehicle path through the intersection Single structure design.
requires, at a minimum, a painted guidance Traffic signals are unnecessary.
stripe. Lends itself to stage construction.
Not suitable for skewed interchanges.
Adding pedestrian movement to the Disadvantages -
interchange adds a signal phase and reduces Large right-of-way requirements.
efficiency. Weaving may severely limit capacity.
Adding weaving lanes on and under structure
Cloverleaf
increase cost.
High weave volumes require collector
The cloverleaf is a four-leg interchange that uses
distributor roads.
loop ramps to eliminate the four left-turn
movements and uses outer ramps for the four Double exit on the expressway complicates
right-turn movements (Figure 500.04). An signing.
interchange with loops in all quadrants is referred Insufficient deceleration length from
to as "full cloverleaf" and all others as a "partial expressway speed to control speed of inner
cloverleaf (parclo)". loop.
Poor safety features.
Application - Where there is a need to avoid Extra travel distance/time required for left
restrictive at-grade left turns and adequate right turns.
of way is available. Large trucks may experience problems with
tight curves.
Part 2 500-4
ROADWAY DESIGN MANUAL Roads and Bridges
General Advantages -
Suitable for stage construction.
Figure 500.05
Cloverleaf with Collector Distributor Road Exit terminals in advance of structure.
Weaving eliminated.
Single exit simplifies signing.
Application - Same as for basic cloverleaf except Expandable if structure opening wide
is more suitable for areas with high weaving enough.
volumes. Can be configured to optimize traffic
volume/capacity.
Advantages - Future expansion if structure opening wide
Minimizes weaving conflicts by placing enough.
weave on collector distributor road.
Minimizes signing difficulties. General Disadvantages -
Provides a single exit and entrance from Minor road has stop condition for left-turn.
main roadway. Minor road may require left-turn storage.
Reduce merging and diverging points on Points of conflict on the minor roadway at
main roadway. the ramp terminals limit capacity and safety.
Higher volume than basic cloverleaf design. Right-turn expressway traffic stops at minor
roadway.
Part 2 500-5
ROADWAY DESIGN MANUAL Roads and Bridges
Advantages - Disadvantages -
Entrance ramp loops. Stop condition on minor road and ramps for
Disadvantages - left turns.
Stop condition on minor road and ramps for Expressway traffic exits onto small radius
left turns. loop.
Advantages - Advantages -
Stop for left-turns confined to movements Stop condition for left turns confined to
from ramps only. movements from minor roadway only.
Entrance ramp loops. Not conducive to wrong-way movements.
Disadvantages -
Expressway traffic exits onto small radius
loop.
Directional Interchanges
A direct connection is defined as a one-way
roadway that does not deviate greatly from -the
intended direction of travel. Interchanges that
use direct connections for the major left-turn
movements are termed directional interchanges
(Figure 500.11). Direct connections for one or
Figure 500.08 all left-turn movements would qualify an
interchange to be termed directional even if the
Disadvantages - minor left turn movements are accommodated on
Stop condition on minor road and ramps for loops.
left turns.
Expressway traffic exits onto small radius
loop.
Entrance/exit loops
Part 2 500-6
ROADWAY DESIGN MANUAL Roads and Bridges
Disadvantages -
High construction costs.
Require detailed, time-consuming study.
Part 2 500-7
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 500-8
ROADWAY DESIGN MANUAL Roads and Bridges
The reduction may be made at a two-lane exit These speeds do not apply to ramp terminals,
ramp or between interchanges. The lane-drop which should be designed using the intersecting
taper should be on a horizontal tangent on the roadway speed.
approach side of a crest vertical curve, or on a
sag vertical curve. The lane reduction shall be Profile - A typical ramp profile consists of the
made on the right using a desirable taper rate of ramp body on an appreciable grade, between
70:1 (minimum taper rate of 50:1). vertical curves that connect to the intersection
legs. The profile at the ramp terminal is
Weaving Sections - Weaving sections are generally determined by the cross road.
roadway segments where vehicles entering and
leaving at adjacent access points cross each Ramp grades should be as flat as feasible. Down
others paths. Weaving sections reduce grades should be limited to 3 or 4 percent on
interchange capacity and should be eliminated ramps with sharp horizontal curvature and
from the main facility where feasible. Refer to significant heavy truck or bus traffic. However,
the Highway Capacity Manual for further sight distance is more important than a specific
discussion on weaving sections. gradient control and should be favored in design.
As general criteria, it is desirable that ascending
507 RAMP DESIGN STANDARDS gradients on ramps be limited to:
Part 2 500-9
ROADWAY DESIGN MANUAL Roads and Bridges
Gores - The term "gore" indicates an area Lane Drops - Typically the ramp lane reduction
downstream from the shoulder intersection points shall be made using a desirable taper rate of 70:1,
as illustrated in Figure 500.12. The gore nose is 50:1 maximum.
defined as that point where the distance
measured between the main line and ramp Lane drop tapers should not extend beyond the 2
travelled ways is 7.0 m. If feasible, the unpaved meter point (the beginning of the weaving
area beyond the nose should be graded level with length) without the provision of an auxiliary
the roadways. Heavy sign supports, street lights, lane.
and roadway structure supports shall be kept out
of the graded gore area. Lane Additions - Lane additions to ramps shall
use a taper rate of 10:1.
Profile grade considerations are of particular
concern through entrance and exit gore areas. In Superelevation And Cross Slope - The factors
some instances the ramp profile, or the controlling superelevation rates discussed in Part
combination of profile and cross slope, is 2, Section 200, Geometric Design Standards,
sufficiently different from the freeway through apply to ramps. Ramp superelevation rates shall
lanes that grade breaks across the gore become be per Table 200.04.
necessary. Where adjacent lanes or lanes and
gore areas at freeway entrances and exits are not Where feasible, the curve radius should be
in the same plane, the algebraic difference in increased to reduce the required standard
pavement cross slope shall not exceed 5%. superelevation rate. Both the edge of travelled
way and the edge of shoulder should be
examined at ramp junctions to assure a smooth
transition.
Figure 500.12
Typical Gore Area
From AASHTO, 1994, A Policy on Geometric Design of Highways and Streets
Part 2 500-10
ROADWAY DESIGN MANUAL Roads and Bridges
Widening - Where ramps have curve radii of 90 facilitate acceleration and merging. Where the
m or less with a central angle greater than 60 loop ramp has a small radius on a steep descent
degrees the lane furthest to the right of the ramp, (over 6%), it is important to develop the standard
shall be widened in accordance with Table 2/3 full superelevation rate by the beginning of
500.03 in order to accommodate large truck the curve. On loop entrance ramps this can often
wheel paths. More than one lane may be be facilitated by beginning the ramp with a short
widened if warranted by truck and bus usage. tangent (20 m to 30 m) that diverges from the
cross street at an angle of 4 to 9 degrees. Longer
Table 500.03 tangents are desirable.
Ramp Widening For Trucks
Distance Between Successive On-Ramps - The
Ramp Radius Widening Lane Width minimum distance between two successive
(m) (m) (m) freeway on-ramps should be the distance needed
<40 2.0 5.6 to provide the standard on-ramp acceleration
40 - 44 1.6 5.2 taper shown on Figure 500.13. This distance
45 - 54 1.3 4.9 should be about 300 m. If the upstream ramp
55 - 64 0.9 4.5 adds an auxiliary lane, the downstream ramp
65 - 74 0.6 4.2 should merge with the auxiliary lane. The
75 - 90 0.3 3.9 distance between on-ramp noses will then be
>90 0 3.6 controlled by interchange geometry.
For ramps having curve radii of 90 m or less
with a central angle greater than 60 degrees. Distance Between Successive Exits - The
minimum distance between successive exit
ramps for guide signing should be 300 m on the
Normally, loop ramps are one lane unless
freeway and 180 m on collector-distributor roads.
capacity warrants additional lanes.
Consideration should be given to providing a
directional ramp when loop volumes exceed 508 ENTRANCE/ EXIT RAMP
1500 vehicles per hour. If multiple lanes are DESIGN STANDARDS
provided, normally only the right lane needs to
be widened. General - The ramp entrance/exit is that ramp
portion adjacent to the through travelled way,
Loop Ramps - Radii for loop ramps should including speed-change lanes, tapers, and
normally range from 45 m to 60 m. Increasing islands. All freeway entrances and exits shall
the radii beyond 60 m is typically not cost connect to the right of through traffic. The
effective as the slight increase in design speed is following paragraphs discuss various design
usually outweighed by the increased right of way elements of ramp entrances/exits.
requirements and the increased travel distance.
For roadway design speeds greater than 80 kph Entrance/Exit Sight Distance - Decision sight
the loop design speed should not be less than 40 distance is desirable along the freeway prior to
kph (45 m radius). Extremely tight curves (less an exit nose and the entire exit terminal should
than 35 m radii) should be avoided because they be visible.
lead to increased off-tracking and increase the
potential for vehicles to enter the curve with When an exit must be located where visibility is
excessive speed. See Table 200.05 for further limited by physical restrictions which cannot be
guidelines on radius versus design speed. corrected by cut widening or object removal, an
auxiliary lane in advance of the exit should be
Research indicates that trucks often enter loops provided. The minimum length of auxiliary lane
with excessive speed, either due to inadequate shall be 300 m desirable, 180 m minimum.
deceleration on exit ramps or due to driver
efforts to maintain speed on entrance ramps to
Part 2 500-11
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 500.13
Single Lane Freeway Entrances and Exits
From Caltrans, 1995, Highway Design Manual
Part 2 500-12
ROADWAY DESIGN MANUAL Roads and Bridges
Exit Design Speed - The minimum design speed Two-Lane Exit Ramps - Where design year
at the exit nose should be 80 kph or greater for estimated volumes exceed 1500 equivalent
both ramps and branch connections. Decision passenger cars per hour, a 2-lane exit per Figure
sight distance should be provided at freeway 500.14 should be used. A minimum 400 m
exits and branch connectors. auxiliary lane should be provided in advance of a
two-lane exit. Provisions should also be made
Entrance Design Speed - The design speed at for widening to three or more lanes at the cross
the nose should be consistent with approach road intersection.
alignment standards. If the approach is a branch
connection or diamond ramp with high alignment For volumes less than 1500 but more than 900, a
standards, the minimum design speed should be one-lane width exit ramp should be provided
80 kph. with provision for adding an auxiliary lane and
an additional lane on the ramp.
Entrance/Exit Designs - Design of freeway
entrances and exits should conform to the Branch Connections - A branch connection
standard designs in Figures 500.13, 500.14, and should be provided when the design year volume
500.15 for single lane, two lane entrances and exceeds 1500 equivalent passenger cars per hour.
exits, and diverging branch connections,
respectively. A branch connection is defined as a Merging branch connections should be designed
multilane connection between two freeways. as shown in Figure 500.14. Diverging branch
connections should be designed as shown in
The minimum deceleration length shown on Figure 500.15. The standard ramp exit connects
Figure 500.13 shall be provided prior to the first to a local street. The diverging branch
curve beyond the exit nose. This provides for connection connects to another freeway and has a
adequate deceleration before entering the curve. flatter angle that allows a higher departure speed.
When the subsequent curve is a descending loop
or hook ramp, or if the upstream condition is a At a branch merge, an 800 m length of auxiliary
sustained downgrade, deceleration length should lane should be provided beyond the merge of one
be increased. (see AASHTO, A Policy on lane of the inlet, except where it does not appear
Geometric Design of Highways and Streets, that capacity on the freeway will be reached until
1994, Chap. X for additional information). five or more years after the 20 year design
period. In this case the length of auxiliary lane
Single-lane Freeway to Freeway Connections should be a minimum of 300 m. For diverging
Freeway-to-freeway connectors may be single connections where less than capacity conditions
lane or multilane. Where design year volume is beyond the design year are anticipated, the length
between 900 and 1500 equivalent passenger cars of auxiliary lane in advance of the exit should be
per hour, initial construction should provide a 400 m.
single lane connection with the capability of
adding an additional lane. Single lane directional Branch Lane Drops - The lane drop taper on a
connectors should be designed using the general freeway-to-freeway connector shall not be less
configurations shown on Figure 500.13, but than 70:1.
utilizing the flatter diverge angle shown in Figure
500.15. Single lane loop connectors may use a
diverge angle of as much as that shown on Figure
500.13 for ramps, if necessary. The choice will
depend upon interchange configuration and
driver expectancy. Single-lane connectors in
excess of 300 m in length should be widened to
two lanes to provide for passing maneuvers.
Part 2 500-13
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 500.14
Two-Lane Entrance and Exit Ramps
From Caltrans, 1995, Highway Design Manual
Part 2 500-14
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 500.15
Diverging Branch Connections
From Caltrans, 1995, Highway Design Manual
Part 2 500-15
ROADWAY DESIGN MANUAL Roads and Bridges
Two-Lane Entrance Ramps - A standard two On curved entrance ramps the distance from the
lane entrance ramp is illustrated in Figure inlet nose (4.25 m point) to the end of the
500.14. This design may be utilized in situations acceleration lane taper should equal the sum of
where the estimated design year volume exceeds the distances shown on Figure 500.13 The 50:1
1500 equivalent passenger cars per hour. Figure taper may be curved to fit the conditions, and the
500.14 includes a minimum 300 m auxiliary lane 1000 m radius curve may be adjusted.
parallel to the freeway, which is only used where
adequate design year capacity exists on the Entrance/ Exit Grades - Grades for freeway
through facility. If capacity is inadequate, entrances and exits are controlled primarily by
consideration should be given to extending the sight distance requirements. Ramp profile grades
auxiliary lane to the next interchange or adding should not exceed 6%.
additional freeway through lanes. For most
Exit Profiles - Vertical curves located just
urban situations, it is recommended that multiple
beyond the exit nose should be designed with a
ramp lanes taper to a single lane prior to the 2-
minimum 80 kph stopping sight distance.
meter separation point (where merging is
Beyond this point, progressively lower design
considered to begin).
speeds may be used to accommodate loop ramps
Entrance/Exit Locations - Freeway entrances and other geometric features.
and exits should be located on tangent sections
Entrance Profiles - Entrance profiles should
wherever possible. This provides maximum
approximately parallel the freeway profile for at
sight distance and optimum traffic operation.
least 30 m prior to the inlet nose to provide
Where it is necessary to locate entrances/exits on intervisibility in merging situations. The vertical
a curve, the ramp entrances and exit tapers curve at the inlet nose should be consistent with
should also be curved. The exit taper radius approach alignment standards.
should approximate the freeway edge of travelled
Where large-truck volumes exceed 20 vehicles
way in order to develop the standard degree of
per hour on ascending entrance ramps with
divergence (Figure 500.16).
sustained upgrades exceeding 2%, a minimum
450 m long auxiliary lane should be provided to
insure satisfactory separating conditions.
Exit Ramp Transitions - Exit ramps in urban
areas may require additional lanes at the cross
road intersection to provide storage and increase
capacity.
If the length of a single lane ramp exceeds 300
m, an additional lane should be provided on the
ramp to permit passing maneuvers.
508.01 RAMP TERMINAL DESIGN
The ramp terminal is defined as the area where
the ramp meets the cross road.
Terminals - Ramp terminals should be treated as
at-grade intersections. The terminal design shall
be per Part 2, Section 400, At-Grade
Intersections, based on near-minimum turning
conditions.
Part 2 500-16
ROADWAY DESIGN MANUAL Roads and Bridges
of the over crossing is 4% or less to avoid movements are allowed within 125 m of the
potential overturning of trucks. ramp intersection.
Terminal Locations - Factors which influence Terminal Sight Distances Horizontal sight
the location of ramp terminals include sight restrictions may be caused by bridge railings,
distance, construction costs, right of way costs, bridge piers, or slopes. Sight distance is
circuitry of travel for left-turn movements, measured between the center of the outside lane
crossroads gradient at ramp intersections, storage approaching the ramp and the eye of the driver of
requirements for left-turn movements off the the ramp vehicle assumed 3.0 m back from the
crossroads, and the proximity of other local road edge of shoulder at the crossroads. Figure
intersections. 500.17 illustrates ramp setback from an over
crossing structure. This figure is based on sight
Where a separate right turn lane is provided at distance being controlled by the bridge rail, but
ramp terminals the turn lane should not continue the same relationship exists for sight distance
as a "free" right unless pedestrian volumes are controlled by bridge piers or slopes.
low, the right turn lane continues as a separate
full width lane for at least 60 m prior to merging, Where ramp set back is unobtainable, sight
and access control is maintained for at least 60 m distance shall be provided by flaring the end of
past the ramp intersection. Provision of the the overcrossing structures or setting back the
"free" right should also be precluded if left turn piers or end slopes of an undercrossing structure.
Figure 500.17
Ramp Setback
From Caltrans, 1995, Highway Design Manual
Part 2 500-17
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 600-1
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 600-2
ROADWAY DESIGN MANUAL Roads and Bridges
In 1986, a major modification was released which The last significant change was in the input
provided a significantly more sophisticated design parameter to use for describing the supporting
and analysis tool. The improvements primarily soil strength. In the 1986 edition, the soil is
were in the areas of failure definition, statistical characterized by the resilient modulus instead of
treatment, and soil characterization. the more nebulous soil support number used in
the 1972 interim method. The resilient modulus
Performance and failure concerns were is a measure of the soil behavior after thousands
incorporated in the 1986 edition by virtue of then of load repetitions, and has come to be widely
longer term monitoring of the pavement sections regarded as the most accurate characterization
in the original test. Pavement condition was variable for pavement design. Climate is directly
added through the Pavement Serviceability Index included in the resilient modulus determination
(PSI), a qualitative evaluation of ride condition through the boundary values used for the test.
using a Likert-type scale. Using this approach, it
is possible to select the amount of condition AASHTO released the final method in 1993. The
change which constitutes failure. A model was most significant changes in the intervening years
developed which linked the change in the (1986-1993) concerned the design method for
pavement condition over time to the usage and overlays and rehabilitation. A major evaluation
environment of the roadway. In addition to of the performance of the design method and its
providing more performance-based design, this underlying assumptions is currently underway in
improvement also allowed life cycle cost analysis. the United States, as part of the Strategic
Highway Research Program (SHRP). This
The underlying concept of life-cycle analysis is to analysis includes detailed observation of nearly
select a pavement solution for the transportation 800 test sections scattered across all parts of the
corridor, rather than for the pavement itself. United States, and an assessment of the ability of
Simply put, the idea is to consider pavement the AASHTO method to predict serviceability and
systems with a lower initial cost (perhaps due to performance. Preliminary results (SHRP, 1994)
thinner pavement) and a higher maintenance cost indicate that while traffic loadings are notoriously
(including overlays) alongside methods with under-predicted (a non-conservative error), the
higher initial costs and lower maintenance costs. results are to some extent offset by severe under-
Because of the serviceability index concept, one prediction of field moduli in the laboratory
can keep track of the changing pavement resilient modulus test (a conservative error). The
performance with time, and thereby determine the major change that is expected in the future will be
timing of major maintenance for economic direct analysis of each potential failure mode,
analyses. Most modern pavement design methods rather than the serviceability approach currently
utilize some form of life cycle analysis. in use, which lumps together many different
failure modes.
Also new in the 1986 interim AASHTO method
was treatment of statistical variability. The The AASHTO method has been modified by
statistical variability of the input parameters and many individual state departments of
pavement performance are incorporated through transportation in the United States. The Arizona
two factors- reliability and standard deviation. Department of Transportation method (ADOT,
The reliability factor accounts for chance 1992) is optimized for the hot climate of the
variation in traffic prediction and performance by southwestern United States. The method is very
allowing the selection of a degree of confidence similar to the AASHTO method, but deals more
that the design will last the design period. The explicitly with the statistical variability of the
higher the desired degree of confidence in the underlying soils. The resilient modulus is the
design, the thicker the pavement. The standard operative soil characterization variable, although
deviation factor accounts for statistical variability due to difficulty in measurement of the resilient
in the input parameters, particularly the traffic modulus ADOT uses a correlation with the
predictions. Hveem Resistance Value (R-value).
Part 2 600-3
ROADWAY DESIGN MANUAL Roads and Bridges
Another method of potential interest is that used same input variables, then one method can be said
by the Ministry of Communications of the to yield a substantially more conservative design
Kingdom of Saudi Arabia (MOC). This is a than the other. In the current case, we will
relatively simple method to apply, in which the compare the SN value for the original TRIP
soil is characterized by the CBR, and the traffic method with the newer design methods using a
by a 16-kip equivalent single axle loading. consistent set of material coefficients.
Design charts are then entered to perform the
actual design. roads are placed into two A SN was developed for each roadway
categories ("Expressways" and "Roads Other classification pavement section described in the
Than Expressways"), allowing some treatment of DCIL TRIP report. The TRIP SN are compared
the desired level of reliability. to the SN resulting from each pavement design
method used in this study in Table 600.02.
Each of these methods incorporates all of the
variables described in the beginning of this Table 600.02
section, with the primary difference being the Comparison of Structural Numbers for
degree to which these variables are explicitly Multiple Design Methods
incorporated in the analytical portion of the
Design Truck Freeway Main Sector
analysis. In general, one can characterize the
Method Route Expressway Road Road
AASHTO method as closest to the analytical end
TRIP 8.40 7.28 5.69 3.31
of the spectrum, and the MOC method as closest
AASHTO 7.9-9.5 7.3-8.9 5.6-6.8 2.8-3.7
to the phenomenological end of the spectrum.
ADOT 7.27 6.90 4.91 2.50
There are methods which are even more heavily
MOC * * * 4.69
weighted towards analysis, but these are most
commonly used for research rather than practice.
The methods described herein are considered *Traffic values too far beyond the range of design
representative of many methods in common use charts to allow extrapolation.
today, and are illustrative of the important factors
in pavement design. The AASHTO results show a range because of
the correlation from CBR to resilient modulus
604.01.02 Comparison of Design Results required for the AASHTO method. A design
CBR of 10 was used for the TRIP design. In
Calculations were performed using the newest order to correlate CBR to resilient modulus,
AASHTO method, the ADOT method, and the AASHTO recommends the equation:
MOC method and compared with the TRIP
method. In order to simplify direct comparison of Mr = 1500(CBR) (Eqn. 1)
results, the comparison was based on Structural
Numbers (SN) which result from each analysis, where-
rather than on a comparison of the pavement Mr = Resilient Modulus (psi)
sections themselves. This approach was used
because the SN is the most useful design CBR = California Bearing Ratio
descriptor which results from the procedures, and
because it is independent of the individual Equation 1 was used to develop the lower SN's
pavement layer components chosen by a given shown in Table 600.02. However, there was
agency. considerable scatter in the correlation between the
CBR and the resilient modulus, with the
High traffic, weak soil, or high degrees of conversion factor ranging to as low a value as
conservatism will all yield higher SN values, and 750. In the absence of actual measured resilient
this number thereby allows direct comparison of moduli with which to evaluate the applicability of
the results of an analysis for similar input the AASHTO conversion, a conservative
variables. For example, if two methods are used approach was adopted in which the design would
that generate vastly different SN values for the be checked with a lower resilient modulus
Part 2 600-4
ROADWAY DESIGN MANUAL Roads and Bridges
corresponding to the lower end of the AASHTO The 1993 AASHTO pavement design method has
correlation range: been used extensively in a variety of climates
across the United States and many other parts of
the world, and has been found to work effectively
Mr = 750(CBR) (Eqn. 2) in a wide range of conditions. The pavement
design method outlined below is based on the
The highest SN shown in each classification for 1993 AASHTO method with modifications
the AASHTO method results from a correlation tailored to local conditions.
to resilient modulus using Equation 2. This range
should capture the range of results likely to result The use of the AASHTO method will allow site
from actual resilient modulus testing. The ADOT specific treatment of individual roads within the
method, which is also based on resilient modulus, Municipality of special importance or roads
was completed using the correlation recommended outside the Municipality on less familiar or less
by AASHTO and presented here as Equation 1. uniform soils. The following method should be
used in conjunction with the 1993 AASHTO
The MOC method was only applicable for the method for all Municipality pavement designs.
lightest roadway classification, the Sector Road.
In every other case, the design equivalent axle 604.02 PAVEMENT DESIGN METHOD
loading for the TRIP roadways was well beyond
the inference space depicted on the MOC design Step 1: Develop Equivalent Single Axle Load,
thickness charts. This result comes about due to W18
the degree of overloading common on TRIP
roadways, rather than to an excessive number of Traffic is represented in the 1993 AASHTO
vehicles. The MOC method is based on a 16-kip method by the equivalent single axle load
axle load, requiring a large destructive effect (ESAL), or the number of 18-kip equivalent
factor when considering that up to 27-kip loads single axle loads that will pass over the pavement
were used in the TRIP report. during its initial service lifetime (typically 20
years). To calculate this value, three components
As can be seen from Table 600.02, there is some are required:
variation in the results based on the method used.
It is readily apparent that the TRIP thickness (1) the number of vehicles which will pass over
results are well within the range of modern the pavement during its lifetime, and
pavement design methods. The TRIP results are (2) the breakdown of those vehicles by weight
well above the ADOT methods and firmly within classification, and
the range of new AASHTO SN's. The method is (3) a means of converting the number of vehicles
non-conservative compared to the MOC method; in each class to an 18-kip equivalent single
however, this comparison is believed to result axle load.
largely from the large truck overloads leading to
huge traffic loadings compared to the 16-kip To estimate the total number of vehicles utilizing
single axle loadings used for design in the MOC. a pavement during its design life, existing and
projected traffic volumes are needed. To
The conclusion is that the major modifications to determine the total number of vehicles, use a
the AASHTO methods which have occurred since straight line interpolation between the existing
the original TRIP method was devised have not traffic volumes and traffic volumes of the design
significantly altered the designs which would be year. For existing pavement studies, calculate the
recommended if the same input variables were average rate between the existing traffic volume
used to start the design process today. The and the traffic volume of the design year. That
suitability of the input variables, both standard average rate is then multiplied by the projected
and road specific, is therefore the most design life of the pavement. For new pavements
appropriate question for the development of a new the number of vehicles would be estimated using
method. Of the methods examined, the 1993 the design period.
AASHTO method is the most appropriate choice.
Part 2 600-5
ROADWAY DESIGN MANUAL Roads and Bridges
The second component, the number of vehicles in Step 2: Develop soil resilient modulus, MR
certain weight classifications comes from detailed
counts of vehicle types in the traffic mix at a The resilient modulus of the soil subgrade is
variety of times and places within each roadway required for design and must be measured or
class. estimated. The AASHTO correlation below gives
reasonable agreement between the California
Finally, a means of converting the rough traffic Bearing Ratio (CBR) and the soil resilient
numbers, broken down by vehicle class, to the 18- modulus. Unless site specific investigations
kip equivalent single axle load is needed. The determine different resilient modulus-CBR
axle load equivalency factors used in the design correlation factors, the AASHTO correlation
method vary with the load on the axle, the type of should be used.
vehicle, and the pavement thickness. See the
AASHTO guidelines for a complete set of tables. Mr = 1500(CBR)
It should be noted that these tables do not reflect where:
the higher tire pressures that are often used in the Mr = Resilient Modulus (psi)
Municipality. However, the tabulated values still CBR = California Bearing Ratio
form a good starting place for equivalency
factors. For a simplified approach, the values in Step 3: Determine the overall standard
Table 600.03 form an acceptable interim deviation, So
approach:
The overall standard deviation is a dimensionless
Table 600.03 parameter that accounts for random variation in
Generic Equivalency Factors the traffic projections and normal variation in the
pavement parameters. Simply put, it provides a
Vehicle Type Equivalency Factor
means of accounting for areas of weaker than
Heavy Truck 6.5
average pavement receiving higher than expected
Medium Truck 1
traffic. A value of 0.45 for So is commonly used
Light Truck .25
for flexible pavement materials.
Automobile .0008
Step 4: Select the level of reliability, R
Using these values and counts or estimations of
traffic loading within the classifications, the The level of reliability describes the degree of
overall 18-kip equivalent single axle loading can certainty that the pavement will last as long as the
be estimated. The advantages of the AASHTO design service period. Statistically, the thicker the
equivalency factor approach outlined above are pavement section the higher the likelihood that the
that (a) the method can be used with very little pavement will last throughout its intended service
data about the traffic composition, or with very life, other factors being equal. The level of
detailed traffic counts; (b) most other methods reliability is represented in the AASHTO equation
require very detailed information about tire by the standard normal deviate, ZR, and in the
pressures, wheel configurations, and load layouts, design nomograph by R. Table 600.04 contains
information which would be even harder to come recommended values for the roadway
by than the traffic counts, and (c) the equivalency classifications. The table contains very
factors can be easily and directly incorporated conservative values to reflect the need for high
within the method. Ideally, detailed weight and performing pavements in a high-growth, low
composition data can be obtained to allow the maintenance management mode.
development of system-specific equivalency
factors, but the AASHTO factors can be used in
the meantime.
Part 2 600-6
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 600-7
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 600-8
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 600-9
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 600.01
Part 2 600-10
ROADWAY DESIGN MANUAL Roads and Bridges
SECTION 700
DRAINAGE
701 GENERAL
Part 2 700-1
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 800-1
ROADWAY DESIGN MANUAL Roads and Bridges
Electricity - Water and Electricity review and give final approval of the project
Department (WED) utility scope of works. The utility planning
Irrigation - Abu Dhabi Municipality process is depicted on Figure 800.01.
Agriculture Section
Sewer - Abu Dhabi Municipality Sewerage 803 SERVICE RESERVATIONS
Projects Committee.
Gas Line - Abu Dhabi National Oil The Departments objective is to locate all utility
Company. services in designated utility corridors or Service
Reservations. This policy applies to all projects
The Utilities Section will provide details on the including new construction and roadway
agency or department responsible for special widening. Service reserves are located for ease of
services such as oil and gas pipelines, 132 KV construction and maintenance and to minimize
and national defense systems. disruption or damage to permanent works caused
by future utility installations or maintenance
Information on existing utilities shall be obtained operations. The reserves are generally located
from the Town Planning Utilities Section, the outside the roadway pavement in parking or
individual Service (Utility) Departments and/or pedestrian areas that are surfaced with removable
the designated Consultant at the beginning of materials including interlocking tiles and precast
design work. This data will include: tile blocks, and asphalt pavements of reduced
thickness. Roadway crossings are perpendicular
Current Service Reservation Locations to the centerline and primarily concentrated at
Distribution of Services intersection locations. The design standards
As-built Drawings require construction of ducts for all existing,
Proposed Facility Plans proposed and future services that cross roadway
pavement. The utility corridors are defined in
This information shall be compiled and analyzed close coordination with the project geometrics and
to ascertain the status of each individual utility. the Town Planning Department. The reserves are
Utility data should be supplemented by field established within geometric criteria that is suited
investigation of the existing facilities including to the installation of pipelines and conduits.
surveys to record structure locations and pipe Alignments are as straight as possible and angle
invert elevations. Manual(by hand) excavation to points limited in severity with the degree of
locate services that are critical to the design deflection ideally corresponding to pipeline
should be performed as necessary. The fittings (22-1/2, 45 degrees).
Consultant will arrange coordination meetings
with the Service Departments to identify utilities The Standard Drawings show several different
to be protected, relocated to the service distributions of standard service reservations.
reservations and new service requirements. The Special reserves for any utilities other than those
service authority may also have plans or projects shown on the standard drawings (CCTV, 132
for utility improvements in progress within the KV, gas, oil.) shall be provided in each project
project limits. with specific approval from the Town Planning
Department. Project design drawings should show
Once the scope of the utility works has been a section view of these special service reserves
defined, the Consultant will prepare separate cost similar to that shown on standard drawings.
estimates of the utility works that are required Deviations from the standard distribution may be
due to conflict with proposed works and new warranted to:
facilities that are proposed for inclusion in the
project by the utility agencies. It is important to Accommodate existing utilities that would not
make a clear distinction between required works otherwise require relocation.
and facility upgrades, since this information will Suit the project geometrics.
be used to determine the extent of the utility Allow for constructability and/or maintenance
works to be included in the project and cost of service facilities with excessive width,
sharing responsibilities. The Department will diameter or depth.
Part 2 800-2
ROADWAY DESIGN MANUAL Roads and Bridges
The final Service Reservation distribution and Separate Plans and Specifications Prepared by
geometry requires the approval of the Town Utility Authority- WED(Electric) and
Planning Department. ETISILAT normally prepare design plans and
specifications for their facilities in-house. WED
804 UTILITY DESIGN develops schematic drawings and estimated
quantities for relocation, protection, salvage and
804.01 GENERAL supply of new cables for inclusion in the tender
documents. The drawings and Bill of Quantities
Utility design requirements will be defined on
are modified as necessary by the authority based
final determination of the scope of utility works
on the results of the manual excavation and issued
by the Department. The final design of each
to Construction. The Contractor will then
utility will proceed based on the existing utility
prepare fully detailed shop drawings for final
information and proposed facility requirements.
approval by the WED.
Refer to the Utilities Procedures Flow Chart,
Figure 800.01.
ETISILAT normally prepares detailed plans and
In general, rapid development, incomplete as-built specifications for the work based on their record
information and the harsh soil conditions make it drawings of the existing telephone system and the
difficult to determine the exact requirements for need for relocation or protection of plant impacted
each service line, especially minor branches and by the improvement project. These drawings are
connections, without the benefit of an extensive normally included with the tender documents.
manual excavation program to locate the utilities. Any necessary adjustments based on manual
As a result, this effort should be accomplished excavation will be done through the shop drawing
during the construction phase to enable process in construction.
preparation of detailed shop drawings that will
fully define the requirements for each utility. The Consultant Prepared Plans and Specifications-
procedure and specifications for this work are The prime Consultant for the improvement
oulined in the Standard Specifications. The project is required to prepare final design plans
tender documents are prepared based on the best and specifications for Surface Drainage, Lighting,
available information and may be limited to the Traffic Control and Drainage/Irrigation. The
major components of a particular service. This designs are prepared in consultation with the
procedure varies with the different utilities and agency or department and the drawings are
generally can be described under three categories: normally prepared as separate documents and
included with the project tender document
Separate Plans and Specifications Prepared by package. Any necessary adjustments based on
Agency Designated Consultant- WED(Water) manual excavation will be done through the shop
and Sanitary Drainage Network Section use a drawing process in construction.
designated Consultant for the design of facilities.
Final design plans, specifications and BOQ are 804.02 UTILITY PROTECTION
prepared as separate documents and included in
the project tender document package. The All utilities under the roadway must be protected.
drawings will indicate the existing facilities This protection will continue under all pavements
anticipated to be protected, relocated or and extend beyond the back of curb, edge of
abandoned as well as new pipeline requirements. shoulder or at the duct end wall constructed at the
Based on the results of the manual excavation, the end of the duct by 0.50 meters. The Standard
Contractor will prepare detailed shop drawings Drawings and General Specifications outline the
that include refinements and adjustments to the type of protection to be used for the various
tender drawings to reflect the conditions utilities consisting of three types:
encountered in the field. The shop drawings
require the approval of the designated Consultant Concrete Slab (Precast or Cast-in-Situ)
and the WED. Concrete Encasement
Split Sleeve Concrete Encased
Part 2 800-3
ROADWAY DESIGN MANUAL Roads and Bridges
These methods are designed to protect the utility conduits may be placed in split ducts and concrete
from induced traffic loading including encased.
construction equipment loads. The Consultant
should check that the depth of existing utilities is Duct bank ends are terminated outside the
sufficiently below the subgrade level to permanent pavement in a reinforced concrete end
accommodate the protection device. wall structure that allows access to the duct ends
without damaging the integrity of the structural
804.03 UTILITY RELOCATION pavement section. These are required at all
multiple duct service reserve crossings. The end
Utility relocation will generally be determined by wall design and details are included in the
the individual utility agency and is subject to Standard Drawings.
approval by the Municipality. Each agency will
supply their relocation design drawings for All duct crossing locations are to be marked in the
inclusion in the Project documents. These field with permanent markers as shown in the
drawings will then be reviewed by the Standard Drawings. These markers are placed at
Municipality to obtain their approval prior to the end of the duct or set in the top of the duct end
inclusion in the Tender Documents. No utilities wall concrete.
other than lighting, underground cables, and
irrigation pipes shall be installed along the central 804.05 UTILITY LOCATIONS
median parallel to the roadway. These lighting
cables and irrigation lines in the median shall be With the exception of lighting cable and irrigation
as close as possible to the curb to avoid distribution lines, there shall be no construction of
disturbance to the greenery. Quantities, except utility lines such as power distribution lines,
for relocation work designed by a designated water lines, sewer lines, storm waterlines or any
utility consultant, shall be calculated by the other lines in the central median of primary roads.
primary Consultant. WED(E) and ETISILAT Utilities of all kinds shall not be constructed
will supply respective relocation quantities. under main roadway asphalt pavement. Utility
lines can be installed in service reserves under
Supply of all the materials required for the sector roads or parking areas where asphalt
relocation works for electrical shall be included in pavement is reduced in thickness.
each contract. Removed and salvaged LV, 11
KV and 33 KV cables excluding joints from site 804.06 NON-DISRUPTIVE ROAD
can be reused for the relocation works if approved CROSSINGS
by the WED. Quantities for the supply and
salvage items shall be as estimated by the WED Utility crossings of completed permanent works,
for each project. All 132 KV cables required for especially Main Roads, Expressways and
the relocation work shall be new and shall be Freeways are to be avoided. Contingency ducts
supplied under each contract. or alternate routes should be used to
accommodate the service requirements whenever
804.04 CONTINGENCY DUCTS possible. When the crossing of primary roadways
is unavoidable, Department policy requires the
Contingency ducts are required at roadway design to specify non-disruptive methods(pipe
crossings for future services to be located in jacking) or tunneling to cross the facility. This
service reserves and at other specific locations should be a performance based specification to
established by the utility authority. Ducts are offer the Contractor flexibility in selecting the
installed where pavements with asphalt or non- equipment and methods.
removable pavers cross over the service reserve.
Part 2 800-4
ROADWAY DESIGN MANUAL Roads and Bridges
Notice of Intent
C Manual Excavation
O As-Built Drawings Tender Drawings
N
Existing Utility Shop Drawings
S
Agency Review
T Consultant Review
R
U Revised Design Drawings - RFC Designated Consultant
C Service Reservations
T
I Utility Works Shop Drawings
O Town Planning Approval Agency Approval
N
Resident Engineer Approval
Designated Consultant
Construction
Record Drawings
Figure 800.01
Utility Procedures Flow Chart
Part 2 800-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 900-1
ROADWAY DESIGN MANUAL Roads and Bridges
Red Violation Camera Loops and foundations A signal head shall be comprised of one signal
locations face only. Typical signal locations shall be as
Closed Circuit Television (CCTV) Poles and follows:
CCTV Controller foundations locations
Pedestrian signals locations and placement 1. A minimum of one signal face shall be
Free Right Turn signal foundation locations provided for each separate vehicular
Pullboxes types and locations movement and a minimum of two signal faces
Cabling requirements and terminations shall be provided for each through or major
Grades for system conduits (ducts) and movement.
location of system detectors 2. Vehicular signals shall be placed in such a
way so as to provide clear visibility to
Local intersection inductive detector loops
approaching traffic. They shall be located no
requirement, design and locations
less than 12 m or no greater than 35 m
Master Controller foundation requirement and
beyond the stopline.
location
Supplemental signal heads shall be used only
Phasing information should be used as a guide in
when warranted, and after a detailed study of the
determining which phases and interval sequences
location is conducted.
shall be provided at a specific location. New
signals should be synchronized with the existing
There shall be one eight-phase, dual ring, single
Arterial Progression System and/or the Central
entry, fully actuated microprocessor based
Computer Control System at the Traffic
controller per intersection interconnected with
Computer Center.
existing systems as required. The controller shall
be equivalent to a menu-driven NEMA type
All traffic signals and associated equipment shall
controller with LCD display capable of operating
be in accordance with the Standard
in a closed loop coordination system.
Specifications. Any variance relating to
equipment type or performance shall be approved
Signal control details including signal plans and
in writing by the Abu Dhabi Municipality.
all traffic signal parameters for signal controller
operation at an intersection/interchange shall be
902.02 SIGNALS, POLES, AND
provided. A note shall be included on the plans
CONTROLLERS
and specifications stating that the control cabinet
is to be wired with the same phase number
Only mast arm signal poles as per the standard
designations as shown on the plans.
drawings shall be utilized. Combination mast arm
signal and lighting poles or poles with multiple
Traffic signal systems shall include inductive loop
mast arms will not be used. All signal lenses shall
detectors with adequate size, shape and number of
be 30 cm including arrow lenses. All signal heads
turns to provide proper actuation. Loop detectors
shall be pole or mast-arm mounted. Span-wire
in bridge decks will normally utilize preformed
mounted signals will not be used.
loop detector material. Saw cutting of detector
loops in newly poured bridge decks will not be
Pedestrian signals will normally be installed in
permitted. Detector loops so located shall be cast
pedestrian pylons. Where appropriate, pedestrian
integral with the bridge deck.
signals shall be installed on the traffic signal pole,
on a street light pole, or on a separate 3.2 m pole.
Separate loop wires for each loop shall be
Pedestrian signals will have two signal sections
provided. There shall be a splice to connect the
with 30 cm lenses. The graphic symbols for
loop wires to the lead-in cable in the curbside
WALK and DONT WALK shall be used.
pullbox. This lead-in cable shall be terminated at
When illuminated, the DONT WALK indication
the detector amplifier in the local intersection
(hand palm) shall be red, and the WALK
controller. There shall be no splices in the lead-in
indication (man walking) shall be green.
cable.
Part 2 900-2
ROADWAY DESIGN MANUAL Roads and Bridges
Where feasible, power feeds for traffic signals If the width of the roadway median at the
should come from two separate substations and intersection is more than 5, but less than 10
be controlled by a changeover switch. This will meters, an additional pylon is placed at the
enable signals to remain functional in the event midpoint of the median with two pedestrian
one of the substations loses power. Separate feed signals back to back. If the median width is more
plans should be developed in cooperation with the than 10 meters, one pylon is placed at each edge
WED. of the median, each with one pedestrian signal.
The signalization design for each intersection Each pedestrian signal is comprised of two signal
shall include as a minimum: units with WALK and DON'T WALK
indications. The DON'T WALK unit, mounted
1. Plan symbols as shown on the standard on top of the WALK unit, has a polycarbonate
drawings. lens with black background and an illuminated
2. A drawing of the overall layout depicting red human hand symbol placed vertically. The
signal pole, detector, signal head and conduit WALK unit, mounted below the DON'T WALK
placements. All vehicular and pedestrian unit, has a polycarbonate lens with black
signal indications shall be labeled by background and an illuminated green walking
movement (signal group) number. man symbol.
3. A drawing including the pole schedule,
detector schedule, clearance times matrix, 903 TRAFFIC SURVEILLANCE
phase movements, and if necessary, notes
specifically corresponding to the design and Communication system facilities shall be installed
installation. on main roads, expressways and freeways. The
4. A drawing showing the conductor schedule. system will communicate traffic conditions to a
5. Additional drawings as necessary for central computer, which will then communicate
installation and materials details. back with the ramp signals, changeable message
signs and TV cameras. Interconnections between
902.03 DUCTS AND PULLBOXES signalized intersections surveillance facilities and
the central computer will be through concrete
All ducts shall be encased in concrete. Based on encased, 4-way or 8-way 10 cm PVC ducts.
the requirement, either 8-way, 4-way, 2-way or 1-
way 10 cm diameter ducts shall be utilized. CCTV cameras are to be located at intervals of
Raceways shall be 2-way 5 cm diameter except approximately one mile. Typical camera locations
for the traffic signal pole foundations raceways will be at interchanges and at midpoint locations
which shall be 3-way 5 cm diameter raceways. between interchanges. To provide for future
Standard pullboxes types (Type I, II and IV) shall implementation, 2 stub-outs of 10 cm diameter
be used as appropriate. schedule 40 PVC conduit, 1 m long, will be
extended from a pull box nearest the midpoint
902.04 PYLONS between interchanges. All conduit shall be
securely capped and locations precisely recorded
Pylons are used to house the pedestrian signals. on as-built plans. The locations, numbers of
Their appearance and materials are meant to add ducts and foundations will be determined from the
color to the streetscape. They are comprised of CCTV Master Plan drawings.
an aluminum tube column base and an aluminum
crown. External color is dark bronze. 904 SIGNING
Pylons with Type B crown are used at all General - Discussion in this section is
signalized intersections where pedestrian signals complimentary to the MUTCD and shall be used
are required unless pedestrian signals can be in conjunction with that document. However,
mounted on nearby light poles. Pylons with Type policies presented in the MUTCD reflect general
B crown are placed within green areas at both practices which may not always be applicable to
ends and at the outer edge of pedestrian crossings. Abu Dhabi. Where there are conflicts between
Part 2 900-3
ROADWAY DESIGN MANUAL Roads and Bridges
this section, the Standard Drawings and the 1. Designating the lane use at forks of major
MUTCD, the guidelines in this section and the inter-city expressway routes.
Standard Drawings should be followed, consistent
with sound engineering practices and judgement. 2. Where roadway and ramp configurations
may be misleading without lane
Traffic signs are installed to regulate, warn, and designations, such as: locations where the
guide road users. Installation, reflectivity, legend through expressway lanes end beyond the
size, legend color, placement, and support type interchange in a terminal, or locations
should all be considered to provide a consistent, where two or more ramps depart from the
safe and informative signing plan. through lanes and require lane use
demarcation for clarity.
904.01 SIGN STRUCTURE
INSTALLATIONS 3. Where lateral space is unavailable for a
ground mounted sign.
904.01.01 Ground Mounted
At interchanges between rural expressways, it is
Ground mounted signs are unobtrusive and can desirable to sign the through expressway lanes in
provide drivers with the essential information in addition to the ramp lanes. This can be
most instances. They are appropriate for marking accomplished with a ground mounted guide sign
all intersections and most interchanges. Typical in the median, if the median is wide enough. If the
guide sign treatments at expressway interchanges median width is inadequate, the through lanes
with main roads are diagrammed in Figure 900.01 guide sign may be cantilevered overhead in the
and Figure 900.02. median. The ramp sign may also be cantilever-
mounted for uniform appearance.
Sign post lengths are to be calculated based upon
the Standard Drawings and the roadway cross Similarly, space for other ground mounted guide
section at the sign locations. Foundations for signs may be restricted, thereby indicating the use
stubs shall be flush with the ground and stub of an overhead cantilever mounting.
protrusions of the concrete foundation shall also
conform to the Standard Drawings. Signs Typical overhead guide sign treatments at major
installed in the median are to be designed for the rural expressway junctions are portrayed in
ultimate roadway section. Figure 900.02.
Part 2 900-4
ROADWAY DESIGN MANUAL Roads and Bridges
interchanges. Existing structures shall be utilized Route markers shall be placed as separate signs
for sign mounting wherever possible. and in conjunction with guide signs as shown in
Figures 900.01 and 900.02. The background used
Bridge Mounted - Sign mounting brackets, for for route markers shall be the falcon symbol
bridge mounted signs, are to be designed based shown below. The sign panel shall have a yellow
upon the criteria set forth in this manual for sizing legend and border on a blue background.
sign panels. Cast-in-place anchor bolts shall be
provided with the bridge structure, together with Guide post types and lengths shall be as per
all the necessary hardware for sign lighting. Figure 900.04 and the Standard Drawings.
Part 2 900-5
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 900.01
Guide Sign Treatment
Interchanges With Main Roads
Part 2 900-6
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 900.02
Guide Sign Treatment
Major Junctions Between Rural Expressways
Part 2 900-7
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 900.03
Sign Installation And Post Selection
Part 2 900-8
ROADWAY DESIGN MANUAL Roads and Bridges
AISC DESIGNATIONS
DIMENSIONS IN CENTIMETERS
TWO POSTS
153,168 Up to 400 A
153,168 401 to 600 B
183,198 Up to 350 A
244,259 Up to 200 A
244,259 201 to 500 B
244,259 501 to 600 C
274,290 Up to 200 A
274,290 201 to 400 B
274,290 401 to 600 C
305,320 Up to 350 B
305,320 351 to 600 C
335,351 Up to 350 B
Figure 900.04
Sign Post Types
Part 2 900-9
ROADWAY DESIGN MANUAL Roads and Bridges
904.05 ARABIC LETTERING FOR GUIDE quite a distance below this baseline; therefore, the
SIGNS vertical spacing on the sign face should be
checked and adjusted, if necessary.
904.05.01 General
Guide signs shall be designed in Arabic and The width of the message Corniche Road is
English, with the Arabic message above the calculated in Example 900-01 on the following
English translation. To size the signs, the actual page. The page numbers refer to the fourteen
width of the Arabic and English messages must pages in the Standard Arabic Script for Highway
be determined. Signs, Section 904.07. Aleph height was assumed
to be 24 cm, slightly larger than the English 20
904.05.02 The Arabic Alphabet cm lettering. Calculations proceed right to left.
The first letter in the Arabic alphabet is aleph Looking at the last letter in the first word, the
which is a simple downstroke. For the purposes of shape extends 43 mm below the baseline. Using
the Standard Script, aleph is used to proportion the proportion of 4.8, at least 20.64 cm will be
the height of the letters. In developing the required between the Arabic and English message
Standard Script, it has been determined that an to avoid conflict.
aleph height of 30 cm generally corresponds to
signing on freeways, while an aleph height of 24 904.06 GUIDE SIGN DIMENSIONS
cm corresponds to signing on arterial roads.
904.06.01 Single Message Guide Signs
Figure 900.05 provides spacing criteria for Guide (Example 900-02)
Sign design. Figures 900.06 through 900.17 are
template guides for Arabic letters and numerals. After computing the preliminary sign width
(message width, arrow width, and offsets) it shall
When designing guide signs for all Abu Dhabi be rounded to the nearest 5 cm to get the final
roadway projects, signs to be read from freeways sign width. Changes to the adjustable base
and expressways will have 30 cm (aleph height) dimensions most likely will have to be made to
Arabic lettering and 27 cm English lettering. achieve this.
Signs to be read from ramps and main roads will
have 24 cm (aleph height) Arabic lettering and 20 Sign faces shall be detailed as per the theoretical
cm English lettering. height dimensions for a particular sign. Small
variations in the spacing between the legend and
904.05.03 Use of the Standard Arabic Script the border can be used to increase or decrease the
overall sign height to an even 50mm increment.
The shape of each letter and number in the However, any reduction shall be limited to 90%
Standard Script is shown on a five-millimeter grid of the original spacing.
in Figures 900.06 through 900.17.
Changes made to achieve the recommended height
To get the actual width of a word on the guide and width shall be spread as evenly as possible
sign, find the width of each letter shape in the over the appropriate adjustable dimensions. If the
Standard Script. Then multiply that width by the preliminary sign height or width is a halfway
proportion of the aleph height in the final guide between two recommended sign heights or widths,
sign to the aleph height shown in the Script. always round to the higher size.
Finally, add the width of each letter shape, taking
into account the spacing rules for unconnected Center the smaller lettering with the center of the
letters to obtain the total message width. wider lettering.
Part 2 900-10
ROADWAY DESIGN MANUAL Roads and Bridges
Proportion: 24 cm = 4.8
5 cm
Example 900-01
Sample Calculation Of Arabic Message Width
Part 2 900-11
ROADWAY DESIGN MANUAL Roads and Bridges
904.06.02 Multiple Message Guide Signs These multiple messages shall be centered
(Example 900-03) with the center of the largest message.
The dimension between two messages shall be
For multiple message guide signs, the rules and
the same as between the Arabic lettering and
base dimensions for a single message guide shall
the upper border stripe on a single message
apply, with a few additions and exceptions.
guide sign.
Guide sign width shall be determined by the The guide arrow shall be vertically centered.
widest message (message width, arrow width and It will also be horizontally offset from the
offsets), measured as if it was a single message largest message as in a single message sign.
guide sign.
Separate guide arrows for each message (multiple
To achieve a recommended height, changes in he messages):
adjustable dimensions should be spread as evenly
as possible throughout all messages. The smaller messages shall not be centered
with largest message, but placed with the
The multiple sign should be shown with a similar same offsets from the guide arrow side of the
dimensional breakdown as the single message sign sign as if they were a single message sign.
(Example 900-02). A single white stripe of 3 or 5 cm shall be
placed between all messages that use separate
The following paragraphs provide guides for use
guide arrows. English and Arabic lettering
with messages containing arrows. Separate guide
shall be offset from this line as from the
arrows for each message:
border stripes in a single message guide sign.
It is preferable to place the guide arrows on
The smaller message shall not be centered
opposite sides of the guide sign.
with the larger message, but placed with the
same offsets from the guide arrow side of the Same guide arrow for multiple messages:
sign as if they were a single message sign.
A single white stripe of 3 cm or 5 cm shall be These multiple messages shall be centered
placed between all messages that use separate with the center of the largest message.
guide arrows. English and Arabic lettering The dimension between two messages shall be
shall be offset from this line as from the the same as between the Arabic lettering and
border stripes in a single message guide sign. the upper border stripe on a single message
It is preferable to place the guide arrows on guide sign.
opposite sides of the guide sign. The guide arrow shall be vertically centered.
It will also be horizontally offset from the
Separate guide arrows for each message:
largest message as in a single message sign.
Part 2 900-12
ROADWAY DESIGN MANUAL Roads and Bridges
24 cm 30 cm
A 3 5
B* 20 27
C 20 27
D (See Note A)
E 24 30
F* 24 30
G* 35 (See Note B) 40
H* 30 (See Note B) 40
J (See Note C)
K (See Note D)
(A) 10 cm + largest distance an Arabic letter in the message goes below the baseline.
* These dimensions may be adjusted to comply with recommended heights and widths.
Example 900-02
Dimensions For Guide Signs
Part 2 900-13
ROADWAY DESIGN MANUAL Roads and Bridges
Example 900-03
Multiple Message Guide Signs
Part 2 900-14
ROADWAY DESIGN MANUAL Roads and Bridges
1 of 14
904.07 STANDARD ARABIC SCRIPT
FOR HIGHWAY SIGNS
Part 2 900-15
ROADWAY DESIGN MANUAL Roads and Bridges
2 of 14
Figure 900.05
Guide Sign Letter Spacing
Part 2 900-16
ROADWAY DESIGN MANUAL Roads and Bridges
3 of 14
Figure 900.06
Guide Sign Lettering
Part 2 900-17
ROADWAY DESIGN MANUAL Roads and Bridges
4 of 14
Figure 900.07
Guide Sign Lettering
Part 2 900-18
ROADWAY DESIGN MANUAL Roads and Bridges
5 of 14
Figure 900.08
Guide Sign Lettering
Part 2 900-19
ROADWAY DESIGN MANUAL Roads and Bridges
6 of 14
Figure 900.09
Guide Sign Lettering
Part 2 900-20
ROADWAY DESIGN MANUAL Roads and Bridges
7 of 14
Figure 900.10
Guide Sign Lettering
Part 2 900-21
ROADWAY DESIGN MANUAL Roads and Bridges
8 of 14
Figure 900.11
Guide Sign Lettering
Part 2 900-22
ROADWAY DESIGN MANUAL Roads and Bridges
9 of 14
Figure 900.12
Guide Sign Lettering
Part 2 900-23
ROADWAY DESIGN MANUAL Roads and Bridges
10 of 14
Figure 900.13
Guide Sign Lettering
Part 2 900-24
ROADWAY DESIGN MANUAL Roads and Bridges
11 of 14
Figure 900.14
Guide Sign Lettering
Part 2 900-25
ROADWAY DESIGN MANUAL Roads and Bridges
12 of 14
Figure 900.15
Guide Sign Lettering
Part 2 900-26
ROADWAY DESIGN MANUAL Roads and Bridges
13 of 14
Figure 900.16
Guide Sign Lettering
Part 2 900-27
ROADWAY DESIGN MANUAL Roads and Bridges
14 of 14
Figure 900.17
Guide Sign Lettering
Part 2 900-28
ROADWAY DESIGN MANUAL Roads and Bridges
904.08 SIGN LIGHTING reflect general practices which may not always be
applicable to Abu Dhabi. Where there are
Roadway sign lighting shall be as recommended conflicts between this section, the Standard
in AASHTOs An Informational Guide for Drawings and the MUTCD, the guidelines in this
Roadway Lighting, 1984, pages 30-32. section and the Standard Drawings should be
followed, consistent with sound engineering
Sign Lighting shall be designed using medium practices and judgment.
ambient illuminance in accordance with the
following table: All pavement markings and symbols shall be
thermoplastic per the Standard Drawings and the
Table 900.01 Standard Specifications.
Sign Lighting
Lighting Medium Ambient Typical urban layouts for pavement markings and
Levels Illuminance raised pavement markers are shown in the
Illuminance 20-40 Fc Standard Plans. Raised pavement markers are
Luminance 48-96 cd/m2 generally not used in rural areas.
Pavement markings shall be used for regulating, For lane marking standards not shown in the
warning, and guiding road users. Discussion in Standard Drawings see Figure 900.18.
this section is complimentary to the Manual on
Uniform Traffic Control Devices (MUTCD) and
shall be used in conjunction with that document.
However, policies presenting in the MUTCD
Part 2 900-29
ROADWAY DESIGN MANUAL Roads and Bridges
905.02.03 Pedestrian Crossing Markings During Construction, existing traffic flow will be
maintained on paved, lighted detour roads. In
Pedestrian crossings shall be marked by general, detours will have two through lanes in
longitudinal stripes through the width of the each direction.
pedestrian crossing which shall be 4.0 m. Stripes
shall be 50 cm wide, with a 50 cm gap between 906.01 CONSTRUCTION STAGING
adjacent stripes.
Construction will be staged so as to avoid
The distance between the upstream edge of the disruption of traffic flow as much as possible.
pedestrian crossing and the beginning of the When required and possible, pedestrian
adjacent stop line shall be 1.0 m. movements will be maintained by temporary
sidewalks.
905.02.04 Channelization Markings
Temporary pavement shall be used for all
All channelization markings, except those detours. Temporary lighting shall be provided
mentioned above, shall be 20 cm wide solid lines. during all stages of construction, including
Dead areas created by channelization will have temporary detours.
chevrons which shall be comprised of 20 cm
continuous line.
Part 2 900-30
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 900-31
ROADWAY DESIGN MANUAL Roads and Bridges
Table 1000.01
Illumination Requirements
Roadway Minimum Uniformity Light Lantern Pole
Illumination Ratio Source Height
(Lux) (m)
Freeways & 22 2:1 HPS Cut-off Type III 30.5
Expressways
Interchanges 22 2:1 HPS Cut-off Type V 30.5 ***
Notes:
1. Lamps for sign lighting should be a different color from roadway. Mercury vapor lamps for sign
lights will provide good contrast and easy differentiation from high pressure sodium roadway
lighting.
2. Recommended illumination level indictates the minimum allowable. Individual designs shall specify
lighting levels as advised by the Municipality/WED at the design phase.
Part 2 1000-2
ROADWAY DESIGN MANUAL Roads and Bridges
criteria and calculations are based on the Lanterns mounted on 10 m poles shall be 400
Illuminating Engineering Societys (I.E.S.) watt high pressure sodium or metal halide
standards modified to meet the higher uniformity lanterns.
and illumination levels required by the WED and
the Municipality of Abu Dhabi. Lanterns shall have optical systems sealed against
moisture, dirt and insects, and be mechanically
Uniformity Ratio strong and easy to maintain.
A Uniformity Ratio (UR) is defined as the
average maintained illumination of the roadway Glare control for the mounting height specified,
design area, divided by the lowest value at any and cut-off characteristics shall be designed based
point in the area. See Table 1000.01 for roadway on I.E.S. standards.
criteria.
Lantern Mounting Height
Light Source High mast lighting (30.5 m) is proposed for
Light sources shall be as identified in Table applicable interchanges and between closely
1000.01 and as modified during the design phase spaced interchanges when conditions permit. On
if advised by the Municipality. It is important major thoroughfares not suitable for high mast
that the lighting design be compatible with the lighting, but where substantial lighting
surrounding area. requirements remain, pole heights would be 14m.
The roadways not identified in this manual will High-mast lighting (30.5 m poles) shall be used
use a light source as directed by the Municipality. on rural and urban freeways and expressways
Side roads and ramps shall have the same light with wide medians where one row of 14 m poles
source as the adjacent main roads. Metal halide is not suitable. The 30.5 m poles shall also be
or high pressure sodium shall be selected to blend used at all interchanges. Wherever possible high
with the surroundings on sector roads. mast lighting shall be used for ramps.
Lantern and Lamp Selection High mast lighting will be used on main roads
Sharp cutoff lanterns are proposed for roadway only when light height will not substantially
lighting per Table 1000.01. These lanterns are interfere with nearby buildings. On other major
designed to illuminate a relatively large area thoroughfares, poles would be 14 m high and
without spilling light into adjacent areas. They would be placed at the side or in the median of the
produce uniform illumination and minimum glare. roadway, as applicable. Single or multiple
lanterns would be used to provide uniform
High pressure sodium lamps provide excellent illumination of the roadway.
golden white color and enhance the esthetic
qualities of concrete, stone and brick. Metal 1002 PARKING AREA LIGHTING
halide gives a whiter light, providing a color
contrast to sodium lamps, and enhance the 1002.01 GENERAL
appearance of green and pastel colored materials.
The function of light sources in parking areas is
The lanterns shall be mechanically strong and to give an overall view of the parking area and
easy to maintain. They shall be of adequate provide a measure of security. Lighting is also
design to operate at mounting heights of 30.5 critical for vehicle maneuvers such as backing.
meters and able to withstand sustained wind
speeds of 160 kph with 208 kph gusts. 1002.02 ILLUMINATION
REQUIREMENTS
Lanterns mounted on 14 meter poles shall be
1000 Watt high pressure sodium, metal halide Light source shall be high pressure sodium or
and mercury vapor lanterns cut-off, and provide metal halide selected to blend with the
efficient even illumination. surroundings per Table 1000.01.
Part 2 1000-3
ROADWAY DESIGN MANUAL Roads and Bridges
Ten meter high poles shall be used for all parking 1004.01 GENERAL
lot areas. Lantern configuration and light
distribution shall be selected to suit the parking These items provide required electrical
area geometry. connections and controls to all roadway lighting,
decorative lighting and street furniture lighting
1002.04 LANTERN SELECTION items (i.e. bus shelters, telephone booths and
sidewalk lights).
Lanterns shall be as detailed in the General
Specifications and Table 1000.01. 1004.02 LIGHTING CONTROLLER
REQUIREMENTS
1003 SIDEWALK LIGHTING
Lighting shall be controlled by a 24 hour timing
1003.01 GENERAL switch. Control cabinet requirements shall be as
specified in the Standard Specifications.
Sidewalk lighting provides visually pleasant and
decorative illumination to sidewalks adjacent to 1004.03 DESIGN STANDARDS AND
buildings, to buildings themselves and to the other PROCEDURES
pedestrian walkways.
Control cabinets should be located in the median
1003.02 ILLUMINATION where feasible. The maximum voltage drop in the
REQUIREMENTS outgoing circuits beginning at the control cabinet
shall be four percent. Branching of underground
Light source will be high pressure sodium per cable circuits from all lighting units except 4.6 m
Table 1000.01 unless otherwise directed by the poles will be allowed. There shall not be any
Municipality. Sidewalk lights will be provided intermediate joints in the lighting cable circuitry
only for the areas specifically advised by the except the terminations in the lighting units or in
Municipality. the junction boxes.
Sidewalk light poles shall generally be 4.6 meters Electric service is 415/240 volts, three-phase,
high with 2-100 watt high pressure sodium four-wire, 50 Hz system furnished by the Water
lanterns. However, special pole heights and and Electricity Department (WED). This service
lantern types may be required to meet special shall be provided at the lighting control cabinets.
situations. The Project Design Manager should Underground distribution to the lighting units
consult the Municipality as to the exact nature of utilizes four conductor and steel wire armored
the requirements at the time of concept planning. XPLE insulated cables. Conductor size will be
25 mm2 for all 30.5 and 14 m light poles and 16
1003.04 LANTERN SELECTION mm2 for all 10 and 4.6 m poles, street furniture
and decorative lighting units. The lanterns will be
Ornamental lighting of proper height for the connected in phase sequence to provide a
pedestrian is proposed for sidewalks along balanced three-phase load.
buildings and in parks and landscaped areas.
Low-level ground lights would be used to
illuminate vegetation.
Part 2 1000-4
ROADWAY DESIGN MANUAL Roads and Bridges
Type IV pull boxes shall be used adjacent to light 1006 DESIGN AND SUPERVISION
pole foundations in paved areas except where RESPONSIBILITIES
interlocking pavers are used. They should be
installed between the foundation race way conduit The Municipality is responsible for the lighting
and the electrical conduit. Cables shall be direct criteria standards to light the roads. This
buried under sidewalks and interlocking pavers criterion covers illumination levels, uniformity
used in parking areas except at the entry or exit of ratios and distribution and differences in
sector roads or parking areas where PVC ducts brightness of the roadways.
shall be provided. Cables under interlocking tiles
at the entry or exit of sector roads and parking WED may suggest/advise of criteria or
areas, shall be through concrete encased PVC improvements in lighting for the Municipality and
ducts. its Consultant to consider in design and
construction. However, WED responsibility is
All PVC conduits and ducts for underground limited to advising of its requirements for
cable lighting circuitry, shall be a minimum of 10 maintenance and access to the lighting poles and
cm diameter. There should be a minimum of one lanterns for inclusion in the Specifications. The
spare duct at each crossing. Where lighting Municipality and its Consultant are responsible
cables are proposed along the service reserves at for adherence to the lighting specifications.
road crossings, the available electrical ducts shall
be used. Separate lighting road crossing ducts are WED is responsible for the technical
not required at these locations. specifications and sizing for the electrical power
supply for the lighting system including
The underground lighting cables shall be installed underground cable circuits, fuses, control
along electrical service reserves in all possible cabinets, pull boxes and conduit. Accordingly,
cases. Wherever the lighting cables are proposed WED will be responsible for review of contractor
outside the service reserve, the cable route shall submittals covering these items during the
be immediately adjacent to the curb line. construction period. WED shall have the right to
inspect such construction in the field and approval
Separate earthing is required only at the terminal by WED shall be required prior to burial of the
pole of each circuitry. All light poles and fixtures underground cable circuitry by the Contractor.
shall be earthed through the cable armoring.
Part 2 1000-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 2 1100-1
ROADWAY DESIGN MANUAL Roads and Bridges
sideslope at one meter (minimum) where the uniform and visually pleasing design and
irrigation line comes out of sleeve. appearance.
6. Ducts should be considered where In general, street furniture will only be provided
maintenance roads and driveways cross in roadway projects at the direction of the Road
irrigation lines. Section. For urban interchange projects,
installation of street furniture will be included as
1103 FENCING part of the proposed improvements. On rural
interchange contracts, the extent of street
The Designer and Abu Dhabi Road Section shall furniture required could range from pedestrian
review fence requirements on a project specific signals to a full compliment of street furniture
basis. elements. On all types of projects, during the
close of the Concept Phase, the Designer should
1104 SLOPE PAVING consult with the Abu Dhabi Road Section to
determine the types of street furniture that should
Slope paving at bridge abutments shall conform be provided.
to the Abu Dhabi Road Section Standard slope
paving details. Descriptions of the basic function, elements,
design standards and procedure for each street
Where the mainline is depressed below the local furniture item are included in following sections.
crossroad, the slope paving shall approximate the
typical cross section contours. A 6 meter grading 1106.02 DESIGN
transition at each edge of the slope paving should
be indicated on the plans. Details of street furniture have been designed and
shown on the Standard Street Furniture Detail
Special treatment of slope paving may be drawings and in the Standard Specifications.
applicable at specific locations. The Designer These details do not have to be revised from one
should coordinate slope paving treatments with contract to the other unless there is a project-
the Abu Dhabi Road Section. specific requirement.
In general, all proposed green areas shall be Benches provide resting facilities for pedestrians,
covered with a 30 cm minimum depth of sweet much needed in Abu Dhabi in view of the warm
sand at the finish grade. climate. There are three types of benches
designed for the Abu Dhabi Roadway Section
The Designer shall calculate the quantity of sweet projects, Type A, Type B and Type C.
sand required for the project. The General Plan
drawings will show the green areas included in the 1106.03.01 Type A bench
project.
This type of bench is comprised of two precast
1106 STREET FURNITURE concrete ends and wood slats (over aluminum
tubes), and does not have a backrest. The Type A
bench is always used in combination with the
1106.01 GENERAL
Type B bench, except when it is used at taxi
stops.
Street furniture to be provided as part of the Abu
Dhabi Roadway Section projects includes
1106.03.02 Type B bench
benches, bus shelters, telephone booths and
sidewalk lighting. The purpose is to provide
This type of bench includes a back rest, a planter
pedestrian amenities and to enhance the urban
and a waste receptacle. Basic elements of the
environment with street furniture that has a
bench itself are the same as the Type A bench,
Part 2 1100-2
ROADWAY DESIGN MANUAL Roads and Bridges
except for the back rest and higher ends. The Bus shelters are to be placed at every bus stop
Type B bench is also used in combination with a except where space limitations prohibit their use.
Type A bench to create a small gathering place They are to be located at the far (downstream,
for a group of people. according to the direction of traffic) end of the
bus stop with one meter from the edge of the
1106.03.03 Type C bench curb.
1. Two combination Type A/Type B benches Etisalat determines locations and quantity of
are placed at every intersection, with each in telephone booths to be included in each Contract
different quadrant (preferably diagonal as approved by the Road Section.
quadrants).
2. If space does not permit the above 1107 NOISE ABATEMENT
arrangement, a Type B bench is placed in the
same fashion. The Designer and the Abu Dhabi Road Section
3. At least two Type B benches are placed at shall review any noise abatement requirements on
each side of the main road between two a project specific basis. In general, the Designer
intersections. is to mitigate, as much as possible, any increase
4. Two Type C benches are placed within each in the traffic noise, especially in residential
bus shelter (considered as part of and paid neighborhoods.
under bus shelters).
5. One Type A bench is placed at each taxi stop. In special circumstances involving sensitive areas,
depressed roadways or noise abatement walls may
1106.04 BUS SHELTERS be required.
Part 2 1100-3
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 100-1
ROADWAY DESIGN MANUAL Roads and Bridges
TunnelA structure carrying a roadway through The design vertical clearance to structures
a hill or mountain. passing over all other highways and streets shall
be at least 5.50 meters over the entire roadway
Pedestrian OverpassA structure carrying a width, including auxiliary lanes and shoulders.
pedestrian walkway over a roadway. An allowance of 150 millimeters is included to
accommodate future resurfacing. This allowance
Pedestrian UnderpassA structure which may be waived if the roadway under the structure
provides for passage of a pedestrian walkway is surfaced with portland cement concrete.
under a roadway.
Certain routes have been designated as truck
102 DESIGN FEATURES routes. On these routes, larger vertical clearance
must be maintained. For future projects, these
102.01 GENERAL routes will be identified by the Abu Dhabi Roads
Section Project Manager during the concept
The general features of design shall be as stage.
specified in Section 2 of AASHTO except as
clarified or modified in this manual. 102.03.02 Pedestrian Overpasses
Part 3 100-2
ROADWAY DESIGN MANUAL Roads and Bridges
The minimum design vertical clearance for Concrete approach slabs shall be used on all
tunnels shall be at least 6.00 meters for freeways structures. Approach slabs serve a dual purpose
and arterials and at least 5.50 meters for all other of providing a transition structure from the bridge
highways and streets. to the approach roadway should the roadway
embankment settle and of eliminating the live load
102.03.05 Sign Structures surcharge of the abutment backwall when the
conditions specified in AASHTO 3.20.4 are
Because of their lesser resistance to impacts, the satisfied. Approach slabs are to be designed
minimum design vertical clearance to sign using the Service Load Design Method and shall
structures shall be 6.00 meters regardless of the cover the entire roadway width including the
highway system classification. An allowance of shoulders, from wingwall to wingwall.
150 millimeters is included to accommodate
future resurfacing. 102.07 ANCHOR SLABS
102.03.06 Width (AASHTO 2.3.1) When approach roadways are paved with
portland cement concrete pavement (PCCP),
The horizontal clear width for rural bridges where adequate means shall be provided to prevent
approach guardrail is used shall provide an pavement growth from causing damage to the
additional width on each side of the approach bridge. Use of a properly designed anchor slab is
roadway width to allow the bridge rail to line up one means of providing such protection
with the approach guardrail. The horizontal clear
width for urban bridges, in which curb and gutter 102.08 DECK DRAINAGE
and/or sidewalks are used, shall equal the
approach roadway width. On grade separation structures, roadway drains
shall not discharge water onto unprotected
102.04 RAILINGS (AASHTO 2.7) embankment slopes or within five meters of the
traveled roadway below, nor shall drains be
In general, concrete barrier should be used as a located less than 1.5 meters from the centerlines
vehicular railing. For situations requiring a of abutments or piers. In urban areas collection
different barrier type, only FHWA crash test of deck drainage in a pipe system may be
approved bridge rails are allowable alternatives. required, with down drains in or on pier columns
discharging into storm drainage collector systems.
Bridge rails shall be constructed vertical. Consideration should always be given to provide
Concrete barriers shall not be slipformed. For collector drains and discharge systems on the
cast-in-place, post-tensioned concrete bridges, approach roadway gutter rather than on the
barriers shall be cast after post-tensioning and bridge.
may be cast before falsework removal.
For bridges with sidewalks, expansion joints shall
102.05 CONCRETE BARRIER be turned up at the curb line to prevent roadway
TRANSITIONS water from entering sidewalk areas. Appropriate
means shall be taken to ensure that sidewalk
Transitions from bridge concrete barrier to drainage does not pond and that the water does
approach guardrail should, when practical, be not escape around the wing walls and erode the
located on the bridge, approach slab or embankment.
wingwalls.
For deck drainage design criteria, refer to the
ROADWAY DESIGN MANUAL - Drainage.
Part 3 100-3
ROADWAY DESIGN MANUAL Roads and Bridges
Wing walls shall extend 1.50 meters beyond the Maximum flexural crack width at the tensile face
catch point, where catch point is defined as the of a reinforced concrete section shall not exceed
intersection of the fill slope in front of the 0.25mm for normal conditions of exposure and
abutment with the finished approach grade at the 0.20mm for marine and unfavorable conditions of
outside face of the wing wall. The bottom of the exposure (such as alternate wetting and drying,
wing walls shall be embedded a minimum of 1 humid atmosphere, direct contact with soil, etc.).
meter into the approach fill at the end of the wing The allowable crack width can be increased by
walls. 25% under earthquake/wind/temporary
construction conditions.
102.10 LIGHTING
102.13 CORROSION PROTECTION
Consideration shall be given to special lighting (AASHTO 8.22)
above and below the structure. This lighting shall
serve as ornamental lighting to enhance the Due to the adverse corrosive environment, all
aesthetics and also to enhance safety. This reinforced concrete structures shall use epoxy
lighting is in additional to the normal roadway coated rebar unless otherwise directed by the
lighting. Refer to the lighting section of this Project Manager.
manual for roadway lighting criteria.
Coordination of all structure lighting with existing 103 ARCHITECTURAL
and/or planned lighting of connecting and CONSIDERATIONS
adjacent roads must be considered.
103.01 PROCEDURE
102.11 BRIDGE DECK ELEVATIONS
Following the approval of the civil and basic
The project design group shall prepare either structural concepts for an interchange, including
computer plotted contours at 0.1 meter intervals configuration, alignment, profile and pier
at a 1:50 scale or tabulate elevations at 3.0 meter locations, the Project Design Manager will meet
intervals along the profile grade line, with with the Structural, Architectural, and Graphics
additional elevation points on each perpendicular Design Managers to develop basic alternatives
(radial) such that the bridge can be completely and set architectural design parameters.
covered with 0.1 meter contours. The number of Environmental constraints and influences will be
elevation points on each perpendicular must be established. The Concept Design Team will
such that the lowest, or the highest, point is determine the number of structural concepts and
outside the bridge for use by the construction architectural options to be studied. The purpose
supervision staff to help check the contractors of these studies will be do develop applicable
geometric layout. concepts and options in the form of presentation
displays, to be used as a basis for the Abu Dhabi
Roads Section review and decision making. The
approved displays are submitted to the Abu
Dhabi Roads Section for review and selection of
the desired alternative. The approved scheme the
will progress to the preliminary and final design
phases.
Part 3 100-4
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 100-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 200-1
ROADWAY DESIGN MANUAL Roads and Bridges
Direction of Flow the bridge in the stream width. Local pier and
abutment scour occurs locally at substructure
For design for the most critical flow and the units due to the turbulence caused by the presence
superflood condition, the following criteria shall of the substructure unit.
be used unless more severe criteria is
recommended in the Drainage Report. Bridges over natural water courses shall be
investigated for four different streambed ground
Design calculations of stream forces on piers over lines. Refer to Figure 200.01 for an illustration
natural water courses shall assume a 0.6 meter of these cases.
increase in pier width per side due to blockage by
debris with a shape factor k = 1.40 for the first Case 1 represents the as-constructed stream
3.5 meters of depth. For flows with depths cross section. For this case, the bridge shall be
greater than 3.5 meters, only the top 3.5 meters designed to withstand the forces from the
shall be assumed blocked by debris with lower AASHTO Groups I to VII load combinations.
sections using the actual pier width and a shape
factor in accordance with AASHTO. For Case 2 represents the long term dry streambed
uncased drilled shafts, a 20% increase in diameter cross section, i.e. the as-constructed stream
should be assumed to account for possible cross section minus the depth of the general
oversizing of the hole and any irregular shape. scour. For this case, the bridge shall be designed
The force distribution on the pier shall be to withstand the same forces as for Case 1. The
assumed to vary linearly from the value at the requirements contained in AASHTO 4.4.5.2 need
water surface to zero at the bottom of the scour not be met.
hole as described in AASHTO.
Case 3 represents the streambed cross section
When the clear distance between columns or condition for the most critical design flow.
shafts is 5.00 meters or greater, each column or Abutment protection is designed to withstand this
shaft shall be treated as an independent unit for event and abutments may be assumed to be
stream forces and debris. When the clear distance protected from scour for this condition. Piers will
is less than 5.00 meters the greater of the two experience the full general and critical flow local
following criteria shall be used: 1) Each column scour. For this case, the bridge shall be designed
or shaft acting as an independent unit or 2) All to withstand the forces from the AASHTO
columns or shafts acting as one totally clogged Groups I to VI load combinations.
unit with 0.6 meters of debris normal to the flow
added on each end. Case 4 represents the streambed cross section
conditions for the superflood condition. For this
The average main channel velocity for the case, all bank protection and approach
appropriate flow condition shall be used in embankments are assumed to have failed.
calculating the stream forces. The water surface Abutments and piers should be designed for the
elevation shall be the high water elevation for the superflood scour assuming all substructure units
appropriate flow condition. A minimum angle of have experienced the maximum scour
attack of 15 degrees shall be assumed. simultaneously. For this case, the bridge shall be
designed to withstand the following forces: DL +
Scour may be categorized into two main types: SF + B + 0.5W. For members designed using the
general and local. General scour is the permanent WSD Method an allowable overstress of 140%
loss of soil due to degradation or mining while shall be used. For members designed using the
local scour is the temporary loss of soil during a LFD Method a gamma factor of 1.25 shall be
peak flow. Local scour may consist of two types: used.
contraction scour and local pier or abutment
scour. Contraction scour occurs uniformly across
Part 3 200-2
ROADWAY DESIGN MANUAL Roads and Bridges
Figure 200.01
Groundline Variations Due to Scour
Part 3 200-3
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 200-4
ROADWAY DESIGN MANUAL Roads and Bridges
Adequate means shall be used to ensure that the 10% due to excess weight.
ties are adequately protected from corrosion. the 5% due to misplaced rebar
rod, nut and bearing plate shall be galvanized in 5% structure behavior approximation
accordance with ASTM A153 (AASHTO M- 10% stress increase (actual vs. calcs.)
232). 30% Total variation assumed to occur
concurrently at the section most
202.06 LIVE LOAD DISTRIBUTION heavily stressed.
(AASHTO 3.6.3 AND 3.12.1)
2. (Beta) Factor
In designing the superstructure, the live load
distribution factors shall not be reduced for The second factor, (beta), is a measure of the
multiple lanes as specified in AASHTO 3.12.1 or accuracy with which we can predict various kinds
rounded to a whole number as specified in of loads. It also reflects the probability of one
AASHTO 3.6.3. These two reductions apply to loads simultaneous application with others in a
substructure design only. combination. It applies separately, with different
magnitudes, to different loads in a combination.
203 LOAD FACTORS For example, it is usually 1.0 for dead load. It
varies from 1.0 to 1.67 for live loads and impact.
An essential feature of Load Factor Design (LFD)
requires raw design loads or related internal Due regard has been given to sign in assigning
moments and forces to be modified by specified values to beta factors, as one type of loading may
load factors (, gamma and , beta), and produce effects of opposite sense to that produced
computed material strengths to be reduced by by another type. The load combinations with
specified reduction factor (, phi). D=0.75 are specifically included for the case
where a higher dead load reduces the effects of
These are safety factors which ensure certain other loads.
margins for variation. The three different kinds
of factors are each set up for a distinct purpose,
each independent of the other two. In this way,
any one of them may be refined in the future
without disturbing the other two.
Part 3 200-5
ROADWAY DESIGN MANUAL Roads and Bridges
3. (Phi) Factor
Part 3 200-6
ROADWAY DESIGN MANUAL Roads and Bridges
Reinforced concrete box girder diaphragm criteria All reinforcing bars are to be epoxy coated bars.
shall be the same as for post-tensioned box All reinforcing bars shall be straight bars top and
girders as specified under Diaphragms in Section bottom. The use of truss bars will not be
402.06 of this manual. permitted.
Part 3 300-1
ROADWAY DESIGN MANUAL Roads and Bridges
For skews less than or equal to 20 degrees the 302.03 PROTECTION AGAINST
transverse bars shall be placed parallel to the CORROSION
skew. For skews greater than 20 degrees the (AASHTO 8.22.1)
transverse bars shall be placed normal to the
girders. The minimum clearance for top reinforcing in
new decks shall be 50 millimeters with 50
Use of steel stay-in-place forms should be millimeter Asphaltic wearing surface and the
considered during design for steel girder or minimum specified concrete strength (f c) shall
precast girder bridges for special conditions only. be 280 kg/cm2.
Some circumstances which warrant such
investigation include: bridges over heavily 302.04 DISTRIBUTION METHOD
traveled roads, bridges over live streams and (AASHTO 3.24.3)
bridges over deep canyons. A discussion on their
use shall be made in the Design Concept Report. Use the AASHTO method for load distribution
If use of steel stay-in-place forms is not on slabs except for unusual loads or unusual
recommended during design, they will not be structures such as single cell boxes.
allowed during construction due to the extra dead
load. Contractor requests for usage during 302.05 RAILING LOADS
construction will not be approved. (AASHTO 3.24.5.2)
302.01 SPAN LENGTHS When barriers are located at the deck edge, the
(AASHTO 3.24.1.2) deck shall be designed to resist both the axial
force and the bending moments due to all dead
The deck slab span length for AASHTO loads and horizontal rail load or due to all dead
girders shall be the clear distance between the loads plus vertical wheel loads, whichever is
top flanges plus one-half the flange width. critical.
Slab Thickness
S(m) t(mm)
Up to 1.800 190
1.801 to 2.100 200
2.101 to 2.400 210
2.401 to 2.700 220
2.701 to 3.000 230
3.001 to 3.300 240
3.301 to 3.600 250
3.601 to 3.900 260
Part 3 300-2
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 400-1
ROADWAY DESIGN MANUAL Roads and Bridges
402 POST TENSIONED BOX normal to girder for sloping exterior webs).
GIRDER BRIDGES Interior webs shall be constructed vertical.
Post-Tensioned Box Girder Bridges shall be A single 250 millimeter thick intermediate
designed in accordance with AASHTO diaphragm shall be placed at the midspan for all
specifications. Girders shall be designed by bridges. Special consideration for additional
Working Stress Method and checked by the diaphragms should be given to box girders with
Ultimate Strength Method (Load Factor Design). large skews, curved boxes and boxes over 2
The deck slab is to be designed by the Working meters in depth. Diaphragms shall be placed
Stress Method. parallel to abutments and piers for skews less
than or equal to 20 degrees and normal to girders
402.02 CONCRETE and staggered for skews over 20 degrees.
(AASHTO 9.2 AND 9.22) Diaphragms shall be cast integral with girder
The following concrete strengths are the desired webs.
strengths to be used. Higher strengths may be
used if approved by the Abu Dhabi Roads Section 402.07 DEFLECTIONS (AASHTO 9.11)
Project Manager.
The deflection shall be calculated using dead load
Initial 2
f c = 290 kg/cm minimum. including barriers, but not the future wearing
surface, gross section properties and calculated
Final f c = 350 kg/cm2 minimum final losses. The additional long term deflection
f c = 420 kg/cm2 maximum shall be calculated by multiplying the deflection
by two. An additional parabolic shaped
402.03 BEARING PADS deflection with a peak equal to 30 millimeters per
100 meters should be added to the total deflection
Allow an extra 80mm movement per 100 meters for simple spans. The final long term deflection
of girder length for long-term creep and shall be the sum of the deflection, the additional
shortening due to post-tensioning. long term deflection and the additional deflection
for simple spans. The camber shown on the plans
402.04 CREEP AND SHRINKAGE shall be the final long term deflection.
(AASHTO 9.4)
Part 3 400-2
ROADWAY DESIGN MANUAL Roads and Bridges
Special consideration shall be given to bridges Calculations shall include the shear due to
supported on falsework with large openings where secondary moment and cable shear. For curved
deflections could be harmful to the structure. box girder bridges, the shear due to torsion shall
Unless falsework requirements are strengthened be included.
or other means taken to ensure the bridge does not
form tension cracks prior to tensioning, the 402.13 FLANGE REINFORCEMENT
maximum allowable tension in a precompressed (AASHTO 9.24)
tensile zone shall be limited to zero.
Reinforcing in the bottom slab of box girders
402.10 LOSS OF PRESTRESS shall conform to the provisions of AASHTO
(AASHTO 9.16) 8.17.2.3 except that the minimum distributed
reinforcing in the bottom flanges parallel to the
For multi-span bridges, the cable path should girders as specified in AASHTO 8.17.2.3.1 shall
have its low point at the midspan. Design should be modified to be 0.30 percent of the flange area.
be based on usage of galvanized rigid ducts with
K = 0.00000066 and = 0.25. Anchor set losses 402.14 METHOD OF ANALYSIS
should be based on 16 millimeter set.
The superstructure may be designed using the
For creep of concrete, the variable fcds should be system as described below:
calculated using the total dead load applied after 1) The bottom slab, in the vicinity of the
prestressing, including the 120 kg/m2 future intermediate support, may be flared to
wearing surface. increase its thickness at the face of the
support when the required concrete strength
402.11 FLEXURAL STRENGTH exceeds 320 kg/cm2. When thickened, the
(AASHTO 9.17) bottom slab thickness should be increased by
In determining the negative ultimate moment a minimum of 50 percent. The length of the
capacity, the top layer of temperature and flare should be at least one-tenth of the span
shrinkage and bottom layer of distribution length (measured from the center of the
reinforcing may be used. In determining the support) unless design computations indicate
positive ultimate moment capacity, the that a longer flare is required.
longitudinal flange reinforcing (AASHTO 9.24) 2) Section properties at the face of the support
may be used. should be used throughout the support; i.e.
the solid cap properties should not be
402.12 SHEAR (AASHTO 9.20) included in the model.
Girder webs will be designed for shear using the 3) Negative moments should be reduced to
Ultimate Strength Method according to the 1979 reflect the effect of the width of the integral
Interim AASHTO Standard Specifications. The support.
maximum girder web stirrup spacing will be 300
mm within 6 meters from the front face of the 4) Dead load forces should not produce any
abutment diaphragms. This will eliminate the tension in the extreme fibers of the
need for re-spacing the web stirrups at the point superstructure.
of web flare if the post-tensioning system requires
flaring. 5) The superstructure should be designed as a
unit with the number of live loads applied in
The value of "d" to be used in shear calculations accordance with Section 202.02 of this
shall be the larger of the calculated "d" value or manual.
0.8 times the overall effective depth.
For box girders with severe sloping webs or
Horizontal shear shall be investigated in boxes over 2 meter deep, transverse flange
accordance with the provisions of AASHTO forces induced by laterally inclined longitudinal
9.20.4. post-tensioning shall be considered in the design.
Part 3 400-3
ROADWAY DESIGN MANUAL Roads and Bridges
Single span structures should be jacked from one The Release Deflection equals the deflection the
end only. Symmetrical two span structures may prestress girder undergoes at the time of strand
be jacked from one end only or jacked from both release. The Release Deflection includes the dead
ends. Unsymmetrical bridges should be jacked load of the girder and the release prestressing
from one end or both ends as required by the force (including the effects of elastic shortening).
design. Three span or longer structures should
be jacked from both ends. The Initial Deflection equals the deflection the
prestress girder undergoes at the time of erection
Several prestressing systems should be checked prior to the diaphragm or deck pours. The Initial
to verify that the eccentricity and anchorage Deflection includes the deflection due to the dead
details will work. In determining the center of load of the girder, the initial prestressing and the
gravity of the strands, the Z factor, the difference effects of creep and shrinkage up to the time of
between the center of gravity of the strands and erection. The time of erection should be assumed
the center of the ducts, shall be considered. For to be 60 days after release.
structures over 120 meters in length, in
determining the c.g. of the strands, the diameter The Final Deflection equals the deflection due to
of the ducts should be oversized by 13 the dead load of the deck slab, diaphragms and
millimeters to allow for ease of pulling the barriers and the effects of long term creep on the
strands. composite girders. The effects of the 120 kg/m2
future wearing surface shall be excluded from
For horizontally curved bridges, special care deflection calculations.
shall be taken in detailing stirrups and duct ties.
Friction losses should be based on both vertical Minimum build-up at the edge of Type III girders
and horizontal curvatures. In designing for and smaller shall be 15 millimeters. For Type IV,
horizontal curvature, the exterior web with the V and VI girders the minimum build-up shall be
smallest radius shall be used. Consideration to 25 millimeters. This minimum build-up at the
the 5% variation allowed per web shall be critical section will ensure that the flange of the
included. girder will not encroach into the gross depth of
the slab.
403 PRECAST PRESTRESSED
CONCRETE The tops of the erected girders shall be surveyed
in the field prior to placement of the deck
403.01 CONCRETE (AASHTO 9.2) forming. If the tops of the erected girder
elevations are higher than the finish grade plus
Concrete for highway structures shall have a camber elevations minus deck slab and buildup
minimum specified initial and final concrete thickness, adjustments will have to be made in the
strengths as shown below. Higher strength roadway profile or in the girder seat elevations.
concrete may only be used when required by Encroachment into the slab of up to 15
design and when approved. millimeters will be allowed for random
occurrences.
Initial f ci = 290 kg/cm2 Min
f ci = 320 kg/cm2 Max 403.03 ALLOWABLE STRESSES-
PRESTRESSING STEEL
Final f c = 360 kg/cm2 Min (AASHTO 9.15.1)
f c = 420 kg/cm2 Max
For pretensioned members, overstressing the
prestressing steel above the initial stressing limit
403.02 DEFLECTIONS (AASHTO 9.11)
for short periods of time to offset seating losses is
not permitted.
The Release, Initial and Final Deflections shall be
shown on the plans. Deflections shall be shown
in centimeters at the tenth points.
Part 3 400-4
ROADWAY DESIGN MANUAL Roads and Bridges
403.04 ALLOWABLE STRESSES- The location of the harped point of the strand
CONCRETE (AASHTO 9.15.2) should be located as required by design with the
preferable locations being near the 1/10 of the
In calculating the temporary stress in concrete span as measured from the midspan of the girder.
before losses due to creep and shrinkage, the steel
relaxation prior to release and the elastic 404 PRESTRESSED I-GIRDERS
shortening should be included.
404.01 GENERAL
403.05 LOSS OF PRESTRESS
(AASHTO 9.16) Precast Prestressed I-Girder Bridges shall be
designed in accordance with AASHTO
For creep of concrete, the variable fcds, should be specifications. Girders shall be designed by
calculated using the total dead load applied after Working Stress Method and checked by the
prestressing including the 120 kg/m2 future Ultimate Strength Method (Load Factor Design).
wearing surface. The deck slab is to be designed by the Working
Stress Method using a maximum allowable stress
For girders with required concrete release of Fc = 110 kg/cm, Class K 335.
strengths of 320 kg/cm2 or less, the time of
release may be assumed to be 18 hours. For The slab and diaphragm dead load is to be
specified strengths over 320 kg/cm2 the time of supported by the girders only.
release should be increased accordingly. For
precast girders, the final losses shall include The Girders are to be designed as a composite-
release losses. section, simply-supported beams for Live Load
and Impact and all superimposed dead loads.
The value of relative humidity to be used in Negative moment reinforcement is to be designed
calculating shrinkage losses, shall be the value of over the intermediate supports considering span
relative humidity at the bridge site. continuity and all loads.
403.06 SHEAR (AASHTO 9.20) Continuity designs will include shrinkage and
creep moments as required by AASHTO Article
The value of "d" to be used in shear calculations 9.7.2.1.
shall equal the depth of the beam plus the
effective depth of the slab with a minimum d = 404.02 CONCRETE
0.80 times the overall depth. The shear shall be
calculated assuming full continuity for composite The following concrete strengths are the desired
dead load and live load plus impact. strengths to be used. Higher strengths may be
used if approved by the Abu Dhabi Roads Section
For single span structures, use the shear design Project Manager.
spacing at the 1/4 point for sections from the end
of the beam to the 1/4 point. For continuous Initial f ci = 280 kg/cm minimum.
multi-span structures, use the shear design f ci = 350 kg/cm maximum.
spacing required from the 1/4 point to the pier for
the section from the 1/4 point to the abutment end Note: 350 kg/cm release strengths can be
to obtain a symmetrical reinforcing pattern for all usually obtained within 18 hours, but require 4 to
girders. 6 additional hours for each additional 7 kg/cm
required above 350 kg/cm. Permission is
403.07 METHOD OF ANALYSIS required from the Abu Dhabi Roads Section
Project Manager for release strengths above 350
The dead load shall be assumed to be unsupported kg/cm and final strengths above 420 kg/cm.
and carried by the girders only. Use of masked
strands for debonding shall not be allowed. Final f c = 350 kg/cm minimum
f c = 420 kg/cm maximum
Part 3 400-5
ROADWAY DESIGN MANUAL Roads and Bridges
The maximum allowable stresses are to be in Allow an extra 40 mm movement per 100 meters
accordance with AASHTO except as modified of girder length for long-term creep and
below: shortening due to prestressing.
The theoretical build-up depth shall be ignored for Diaphragms, cast within the beam, shall be
calculation of composite section properties. provided at the midspan for spans up to 15
meters, at the third points for spans from 15 to 22
405 PRESTRESSSED VOIDED SLABS meters and at quarter points for spans over 22
meters.
405.01 END BLOCKS
406.03 LATERAL TIES
End Blocks should be 380 millimeters long with
sufficient steel provided to resist the tensile forces One lateral tie shall be provided through each
due to concentrated prestressing loads. diaphragm located at the mid-depth of the section.
However, for the 990 millimeter and 1065
405.02 DIAPHRAGMS millimeter deep sections, when adjacent units are
tied in pairs for skewed bridges, in lieu of
Diaphragms shall be cast within the slab at continuous ties, two ties shall be provided, located
midspan for spans up to 12 meters and at third at the third points of the section depth.
points for spans over 12 meters.
406.04 SHEAR KEYS
405.03 LATERAL TIES
After shear keys have been filled with an
One lateral tie shall be provided through each approved non-shrink, low slump mortar, lateral
diaphragm located at the mid-depth of the section. ties shall be placed and tightened.
405.05 BARRIERS
Part 3 400-7
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 500-1
ROADWAY DESIGN MANUAL Roads and Bridges
SECTION 600
To allow for the effects of long term creep and
EXPANSION AND
shrinkage in post-tensioned box girder bridges,
CONTRACTION the following additional shortening shall be
included:
601 MOVEMENT CRITERIA
Joints: 40 mm per 100 meters.
601.01 MOVEMENT RATING Bearings: 80 mm per 100 meters.
Part 3 600-1
ROADWAY DESIGN MANUAL Roads and Bridges
Available types of joints include compression list of approved joint types which can be obtained
seals, strip seals, and modular joints. from the Project Manager.
Compression seal joints and strip seal joints are
generic and should be detailed on the plans, by 602.02 COMPRESSION SEALS
standards and/or covered in the special
provisions. Modular joints are proprietary and The compression seal element should have a
require that the designer specify allowable joint shape factor of 1:1 (width to height) to minimize
types and styles in the special provisions. side wall pressure. The size of the compression
Information concerning specific design seal shall be specified on the plans.
parameters and installation details of modular
joints should be obtained from literature supplied Effective movement ratings for this type of joint
by the manufacturer of the system. It is the range up to 50 millimeters. Advantages for this
responsibility of the designer to review the type of joint include its low cost, proven
proprietary joint literature and related performance and acceptance for use on pedestrian
manufacturer's specifications to ensure that the walkways. However, this type of joint can not be
selected joint types are properly specified and unbolted and easily raised, generates pressure and
compatible with the design requirements. is not good for high skews or horizontal
directional changes.
The following features of joints should be shown
on the plans: 602.03 STRIP SEALS
1) Blockout details showing a second pour, Strip seals should generally conform to the details
including blockout dimensions and shown in the structure detail drawing titled "Strip
additional reinforcing required. Seal Joint". Proprietary alternates to this detail
2) Required end treatment in barriers or other than those shown on the detail drawing will
curbs, including enough detail or not be allowed.
explanation to accommodate each of the
proprietary systems selected (i.e. cover Effective movement ratings for this type of joint
plates, etc.). range up to 100 millimeters. This type of joint is
3) Consideration to traffic control in best used when the movement rating is beyond the
determining section pattern lengths. capacity of compression seals and for large
4) Movement rating. skews. Strip seal joints will require cover plates
5) Assumed temperature and opening at time for pedestrian walkways.
of installation with temperature correction
factors. 602.04 MODULAR JOINTS
6) Actual horizontal length of joint measured
from inside of barrier face to inside of Modular joints are very complex joint systems.
barrier face corrected for skew. Effective movement ratings range from 100
millimeters up to 750 millimeters. Modular joints
The following features of joints should be are the best choice for movement ratings over 100
specified in the specifications: millimeters.
Part 3 600-2
ROADWAY DESIGN MANUAL Roads and Bridges
rating should be based on the full temperature due to prestressing is greater than 25 millimeters
range and not the rise or fall from a mean and where the movement rating including elastic
temperature. shortening, long term creep and shrinkage and
temperature is greater than 40 millimeters.
All bearings types except elastomeric bearing Pads shall have a minimum thickness of 25
pads shall be designed for impact. millimeters and be designated in 10 millimeter
increments. The use of elastomeric bearing pads
603.02 NEOPRENE STRIPS should generally be limited to a thickness not
greater than 100 millimeters. Holes will not be
Neoprene strips consist of a sliding plate on a allowed in the pads.
continuous neoprene pad. Where appropriate,
neoprene strips are the preferred bearing type for Width and length dimensions shall be detailed in
post-tensioned box girder bridges. However, even 50 millimeter increments. When used with
neoprene strips are not appropriate for the prestressed I-girders, pads shall be sized a
following applications: curved bridges, skews minimum width of 50 millimeters less than the
greater than 20 degrees, contributing spans nominal width of the girder base to accommodate
greater than 50 meters, where initial shortening the 20 millimeter side chamfer and shall be set
Part 3 600-3
ROADWAY DESIGN MANUAL Roads and Bridges
back 50 millimeters from the end of the girder to appropriate. The pad dimensions and all details
avoid spalling of the girder ends. of the anchorage and restraint systems shall be
shown on the plans. The special provisions
Elastomeric pads should not be used in cases should allow for proprietary alternates.
where deck joints or bearings limit vertical
movements, such as in older style sliding steel Sliding elastomeric bearings should be considered
plate joints or widenings where existing steel for applications where regular elastomeric bearing
bearings are to remain. pads would exceed 100 millimeters in height or
where special access details would be required for
Where elastomeric bearing pads with greased other proprietary bearings in such places as
sliding plates are used on post-tensioned box hinges.
girder bridges to limit the required thickness of
the pad, the pad thickness should be determined 603.06 HIGH-LOAD MULTI-
based on temperature movements only, with the ROTATIONAL BEARINGS
initial and long term shortening assumed to be
taken by the sliding surface. 603.06.01 Description
Elastomeric bearing pads are the preferred High-load multi-rotational fixed bearings consist
bearing type for new steel girders, precast of a rotational element of the Pot-type, Disc-type
prestressed girders and post-tensioned box girder or Spherical-type. High-load multi-rotational
bridges where neoprene strips are not appropriate. expansion bearings consist of a rotational element
of the Pot-type, Disc-type or Spherical-type,
603.04 STEEL BEARINGS sliding surfaces to accommodate translation and
guide bars to limit movement in specified
Steel bearings may consist of rockers or fixed or directions when required.
expansion assemblies which conform to the
requirements specified in Section 10 of Pot bearings consist of a rotational element
AASHTO. comprised of an elastomeric disc totally confined
within a steel cylinder. Disc bearings consist of a
Steel bearings are not a preferred bearing type rotational element comprised of a polyether
and their use should normally be limited to urethane disc confined by upper and lower steel
situations where new bearings are to match the bearing plates and restricted from horizontal
existing bearing type on bridge widening projects. movement by limiting rings and a shear restriction
mechanism. Spherical bearings consist of a
603.05 SLIDING ELASTOMERIC rotational element comprised of a spherical
BEARINGS bottom convex plate and mating spherical top
concave plate.
Sliding elastomeric bearings consist of an upper
steel bearing plate anchored to the superstructure, These design criteria were prepared for the broad
a stainless steel undersurface and an elastomeric range of normal applications and the specified
pad with a teflon coated upper surface. The limits of loads, forces and movements. The
teflon surface shall be attached to a 10 millimeter design and manufacture of multi-rotational
minimum thick plate which is vulcanized to the bearings relies heavily on the principles of
elastomeric pad. The bearing accommodates engineering mechanics and extensive practical
horizontal movement through the teflon sliding experience in bearing design and manufacture.
surface and rotation through the elastomeric Therefore, in special cases where structural
bearing with the thickness of the elastomeric requirements fall outside the normal limits, a
bearing determined by the rotational and friction bearing manufacturer should be consulted.
force requirements. Keepers may be used for
horizontal restraint of the pads. Vertical restraint
may be provided by anchor bolts with slotted
keeper plates or individual vertical restrainers as
Part 3 600-4
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 600-5
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 600-6
ROADWAY DESIGN MANUAL Roads and Bridges
2. Minimum Structure and Construction Restraining devices could include concrete shear
Rotation requirements. keys or end blocks, horizontal or vertical cable
restrainers or mechanical restraining devices
3. Magnitude and direction of movements which could be an integral part of a bearing or a
at all bearing support points. separate system. Restraining devices to prohibit
vertical displacement at expansion ends, shall be
4. Quantity, type (fixed, expansion or designed to allow for inspection and future
guided expansion). replacement of bearings.
5. Plan view, alignment and location of all Allowable restraining devices include, but are not
bearing units. limited to the following: Vertical Fixed
Restrainers, Vertical Expansion Restrainers,
6. Allowable upper and lower bearing External Shear Keys, Internal Shear Keys and
contact pressure. Keyed Hinges.
8. Grades, bevels and slopes of all Vertical fixed restrainers consist of cable and
bearings. appropriate hardware and are designed to allow
Part 3 600-7
ROADWAY DESIGN MANUAL Roads and Bridges
Vertical expansion restrainers consist of cable For a typical expansion seat abutment where
and appropriate hardware and are designed to restraining devices are required, the restraining
allow rotation and longitudinal translation but no devices will consist of vertical expansion
transverse translation. Some limited vertical restrainers and external shear keys.
displacement is allowed to permit replacement of
bearings if required. For a typical pinned seat abutment for a post-
tensioned box girder bridge, restraining devices
604.04 EXTERNAL SHEAR KEYS will consist of vertical fixed restrainers and
external shear keys. For a typical pinned seat
External shear keys are reinforced concrete blocks abutment for a prestressed girder bridge,
designed to limit transverse displacement while restraining devices will consist of vertical fixed
allowing longitudinal and rotational movements. restrainers and external or internal shear keys.
External shear keys are preferred to internal shear
keys since they are more accessible for repairs For a typical expansion pier, restraining devices
and easier to construct. will consist of vertical expansion restrainers and
internal shear keys.
604.05 INTERNAL SHEAR KEYS
For a typical pinned pier, restraining devices will
Internal shear keys are reinforced concrete blocks consist of vertical fixed restrainers and internal
designed to limit transverse displacement while shear keys or a keyed hinge.
allowing longitudinal and rotational movements.
Part 3 600-8
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 700-1
ROADWAY DESIGN MANUAL Roads and Bridges
701.04 DRIVEN PILES For the most part, bored piles will include a
temporary casing or liner intended to preclude the
The Geotechnical Engineer is responsible for intrusion of earth into the hole during the boring
recommending when driven piles are to be used, operation and a permanent casing or liner that
The type of driven pile to be used, the allowable will remain in place and not be withdrawn during
capacity of the pile, the estimated pile tip the concreting process. The temporary casing
elevation and any special requirements necessary will be advanced a sufficient depth into rock to
to drive the piles. When steel piles are used, the provide a seal against water inflow. The
corrosive life of the pile will be reported in the temporary casing shall be clean and free of water
Geotechnical Report. The Geotechnical Engineer before the permanent casings or liners, reinforcing
is also responsible for running the WEAP87 wave steel and concrete are placed.
equation computer program to determine the
driveability of the specified piles and to develop The bridge design group is responsible for
charts or other guidelines to be used by ensuring that the allowable axial capacity is not
construction personnel to control the pile driving exceeded for any AASHTO Group Loading and
process. that the shaft can withstand the applied lateral
loads.
The bridge design group is responsible for
ensuring that the allowable axial capacity is not Unless specified otherwise in the Geotechnical
exceeded for any AASHTO Group Loading and Report, the following minimum criteria should be
that the pile can withstand the applied lateral used in designing bored pile foundations:
loads.
1. Bored Piles shall be spaced a minimum of
701.05 BORED PILES two diameters measured center to center of
the holes plus 100mm.
A bored pile foundation consists of excavating a
round hole by machine, installing a metal casing 2. Temporary and permanent casings or liners
or liner, placing a reinforcing cage in the casing shall be designed to withstand handling
or liner and then filling the casing or liner with stresses, applicable concrete and surrounding
concrete. soil pressures, and shall be watertight.
Part 3 700-2
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 800-1
ROADWAY DESIGN MANUAL Roads and Bridges
The Bridge Design Section is responsible for the 1. The minimum factor of safety against
design of the structural elements of the wall, the overturning
length of the wall and for producing the required 2. The minimum factor of safety against sliding
construction plans, when requested by others, for 3. Maximum coefficient of friction against
any non-proprietary wall requiring structural sliding
analysis. The Bridge Design Section is also 4. Phi angle of the backfill
responsible for determining whether shoring will 5. Allowable bearing pressure
be required during construction based on the 6. Minimum design life
acceptable limits of excavation provided by 7. Water table level
Roadway Design and the safe excavation slopes 8. Elevation of footing bottom
provided by Geotechnical. The Bridge Design 9. Maximum tolerable deflection
Section also selects walls which will handle
differential settlement, when present, and provides
Part 3 800-2
ROADWAY DESIGN MANUAL Roads and Bridges
For all other applications, for steel with a yield 1. Each case will be judged on its own
strength greater than 3360 kg/cm2, the allowable merit with the utilities providing
stresses for design shall be limited to a yield complete justification as to why
strength of 3360 kg/cm2. This limitation alternative locations are not feasible.
indirectly places a limit on allowable deflections 2. Economics will not be a significant
in an attempt to satisfy the criteria of Article factor considered in the feasibility issue.
1.9.1. This limitation also reduces the stresses in 3. Open girder type structures across major
any high strength welds which are more brittle rivers.
and subject to cracking due to fatigue from 4. Pedestrian or utility bridges where
vibrations. proper vented casings and other safety
systems are used.
902 UTILITIES IN STRUCTURES 5. All lines are protected by casements.
Part 3 900-1
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 900-2
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 900-3
ROADWAY DESIGN MANUAL Roads and Bridges
Dhabi Roads Section Project Manager and shall Where the vertical falsework clearance is less
be stated in the Bridge Selection Report. than 4.50 meters, advance warning devices shall
be specified or shown on the plans. Such devices
To establish the grade line of a structure may consist of flashing lights, overhead signs,
spanning an existing street or highway, over-height detectors or a combination of these or
allowance must be made for depth of falsework, other devices. A standard insert sheet has been
where used, to provide the clearance needed to developed for the details of the over-height
permit traffic through the work area during detectors or safety beams. Providing for these
construction. The minimum allowances to be devices in the specifications or on the plans shall
made for depth of falsework shall be as shown in be the responsibility of the Abu Dhabi Roads
Table 900.02 and shall be based on the actual Section Project Manager.
falsework openings determined by the Abu Dhabi
Roads Section Project Manager. Note to bridge designer: Special consideration
shall be given to limit the maximum allowable
The minimum vertical clearance for falsework tension in a precompressed tensile zone of post-
over freeways shall be 4.50 meters. tensioned box girder bridges supported on
falsework with large openings.
Table 900.01
FALSEWORK SPAN REQUIREMENTS
Table 900.02
FALSEWORK DEPTH REQUIREMENTS
Falsework Opening 7.2 8.4 10.8 12.0 14.4 15.6 18.0 19.2
(meters)
Minimum Required
Falsework Depth(mm)
Max 3365 kg/m 485 510 585 815 915 1070 1095 1145
per girder line
3365 - 4580 kg/m 510 560 815 890 1070 1120 1145 1170
per girder line
NOTES:
1. DL based on 2550 kg/m3 concrete.
2. Table 900.02 is based on the superstructure concrete being designed for zero tensile stress at the
falsework openings. Superstructures designed with concrete tensile stresses can significantly
increase the required falsework depths shown in the table and amount of falsework required.
3. Structures with greater than 4580 kg/m Dead Load per girder line will require special
considerations for required falsework depths.
Part 3 900-4
ROADWAY DESIGN MANUAL Roads and Bridges
Part 3 900-5
ROADWAY DESIGN MANUAL Roads and Bridges
904.04 STEEL GIRDER BRIDGES the pier. Their location should be near the point
of dead load counterflexure.
The effects of uplift and allowing a continuous
pour should be considered when developing deck 904.05 CAST-IN-PLACE BOX GIRDER
pour schedules for multi-span continuous steel BRIDGES
girder bridges. The required rate of pour should
be compared to the quantity of concrete to be Box girder bridges made continuous over
placed and the potential for poured sections to set supports shall have transverse construction joints
up and develop tensile stresses from pours in placed so that the webs undergo their positive
adjacent spans shall be considered when moment falsework deflections prior to the final
determining the need for construction joints. pour over the negative moment areas of the fixed
Consideration must be given to the potential for piers or abutments if the superstructure
negative moment stresses in the deck due to formwork is supported on conventional
placement of positive moment pours in adjacent falsework. The transverse construction joints
spans. may be omitted if the superstructure formwork is
supported on earthen fill. The webs and all
Girder bridges will usually require details on the diaphragms should be poured concurrently with
plans showing a plan view with joint locations, the bottom slab. Transverse construction joints
deck pour sequence and direction of pour, if where required should be parallel to the
required. Except where otherwise required, there centerline of the pier. Their location near the
should be a minimum of 12 hours between inflection point is generally one-quarter of the
adjacent pours. Construction joints, where span length from the pier if the adjacent spans
required, should be parallel to the centerline of are approximately equal length.
Part 3 900-6