3.1 Design Elements of At-Grade Intersection
3.1 Design Elements of At-Grade Intersection
3.1 Design Elements of At-Grade Intersection
OUTLINE
1. What is an Intersection
2. Types of Intersection
5. Auxiliary Lanes
6. Turning Roadways
8. Pedestrian Facilities
9. Loading/Unloading Facility
Common/Shared Area
Physical Area
Entry
Approach Exit
Interchange
Roundabout Major street two-way volume (veh/h)
- Number of legs Highway Capacity Manual
Three-leg intersection
Ideal number of legs
Four-leg intersection
(N)-leg intersection
2.1 Types of Intersection – Control Type 1/5
Minor Road
STOP
Major Road
STOP
2.1 Types of Intersection – Control Type 2/5
STOP STOP
STOP STOP
Right-hand Rule
2.1 Types of Intersection – Control Type 3/5
Signalized intersection
Movements are
separated by TIME
Green
indication
has the Right-
Of-Way to
cross the
intersection
2.1 Types of Intersection – Control Type 3/5
Interchange
Movements are
separated by
SPACE
Flyover or
underpass
2.1 Types of Intersection – Control Type 5/5
Roundabout
2.2a Types of Intersection – Number of Legs 1/4
3-Leg Intersection
Single Lane
Approaches
2.2a Types of Intersection – Number of Legs 2/4
3-Leg Intersection
Right-Turn Lane and
Bypass Approaches
Designated Lanes
for Each Movement
2.2a Types of Intersection – Number of Legs 3/4
3-Leg Intersection
With pair of Right-Turn Lane
(Turning Roadway) and
Right-turn Island
3-Leg Intersection
4-Leg Intersection
Plain
4-Leg Intersection
4-Leg Intersection
3-Leg Intersection
4-Leg Intersection
2.2d Types of Intersection – Conflict Points 2/4
4-leg roundabout
2.2d Types of Intersection – Conflict Points 3/4
Example: PULILAN JUNCTION
Channelization
Auxiliary Lanes
Pedestrian
Turning Facility
Inside
Roadways
Intersection Area
Entry Approach
Exit Approach
Entry Approach
Exit Approach
Stop Bar
Directional
Solid White Lane Line Arrow Markings
2nd set
15.0 m 40.0 m
1st set
Double Yellow Barrier No Passing Line
30.0 m
75.00 - 100m
3.0 m
Auxiliary Lanes
L T R
DESIGN ELEMENTS OF AT-GRADE INTERSECTION
4. Turning Roadways
Turning
Roadways
Simple Curve
38
Offset
39
Simple Curve
DESIGN ELEMENTS OF AT-GRADE INTERSECTION
4.1c Minimum edge-of-travelled way design
Edge-of-Traveled-Way Designs for Turns at
Intersec-tions—Three-Centered Curves
Offset
40
Three-Centered-Compound Curve
40
(Symmetric)
DESIGN ELEMENTS OF AT-GRADE INTERSECTION
4.1d Minimum edge-of-travelled way design
Design considerations:
▪ Allows drivers to avoid abrupt deceleration,
▪ Permits development of some super-elevation in advance of
the maximum curvature,
▪ Enables vehicles to follow natural turning paths
Simple Curve,
Radius = 35 m
Compound Curve,
Radii = 70 m and 35 m
Design speed:
20-30 kph < through speed
Intersection
Area
2nd set Directional Arrow Markings 1st set
40.0 m
Transition Line w/ Chevron
Markings
Broken White Transition Lines
Channelization
Pedestrian
Yellow Box
Crosswalk
Placed where Placed directly Usually Requires give- Used May be erected
there are at the stop located in way-to-the- alongside at channelized
dedicated lines or at the conjunction right rule and exclusively signalized
wheel chair approaches to with islands at controls traffic right turning intersections
ramps at stop a zebra channelized at locations lanes where right
lines near or pedestrian intersections such as turning lane is
at crossing Plate type is channelized segregated by
intersections for urban intersections traffic island
areas only
W (min) = 1.20m
M
w = 3.0 – 3.6m
to ensure no
encroachment on
adjacent lanes
Large DESIGN
VEHICLE
SU-9
WB-20
MEDIAN OPENING
DESIGN ELEMENTS OF AT-GRADE INTERSECTION
5.4 Channelization - Median Islands
Minimum design of
median openings
using P design
vehicle
MEDIAN OPENING
DESIGN ELEMENTS OF AT-GRADE INTERSECTION
5.4 Median Islands – Road Signs
Pedestrian
Facility
Continuity of PEDESTRIAN
PATH must be ensured.
W = S = 300-600 mm
L = ≥ 4.0 m
30.0 m 50.0 m
500.0 m
Inside
Intersection Area
B U R E A U O F Q U A L I TY A N D S A F E TY