Effect of Road Geometrics On Accidents
Effect of Road Geometrics On Accidents
Effect of Road Geometrics On Accidents
Asian countries
The latest annual statistics indicate that over 80,000 people are killed on Indian roads
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Pedestrian
Cyclist
Two Wheeler
Four Wheeler
Other
No. of Accidents
325864 284646
150000 100000
114100
64463 70781 74665 76977 7991 9 81 966 7891 1 80888 84674 85998 9261 8
541 00
56278
601 3 1
60380
50000 0
24000 1 4500
70
80
90
91
92
93
94
95
96
97
98
99
00
01
02
03 20
19
19
19
19
19
19
19
19
19
19
19
19
20
20
20
Year
20
04
Year
Total 2001 2002 2003 2004 2005 28902 34133 34826 38937 38339 per Day per Hour in year 79.2 93.5 95.4 106.7 105 3 4 4 4 4 8248 9523 9679 11046 11076
No.of Accidents
9523
9679
11046
11076
2002
2003 Year
2004
2005
No. of Accidents
No. of Deaths
OBJECTIVES
Identifying the Blackspot locations Identify road design elements that affect road safety. Identify how a variation in standards for design elements affects the safety of roads in different environments. Develop models for practitioners to determine the appropriate balance between road design standards, road safety.
STATISTICAL METHODS
This Method summarizes the number of crashes at location and the stretches having the more number of crashes are taken as accident prone stretches Advantages: o Simple to use o Doesnt require additional information beyond number and location of crashes Disadvantage : Traffic volume is not accounted
n: Analysis Time Period, generally taken as 5 years For links 0.6 miles or longer, the DEV is determined using the following equation:
* DEV
4.Frequency-Rate Method
This method is a combination of the Crash Frequency and
Crash Rate Methods. Locations are first ranked by Crash Frequency and the worst locations re-ranked using Crash Rate.
The rational of combining Crash Frequency and Crash Rate is to eliminate or minimize the bias of the two individual methods
calculated and stretch having more accident rate is taken as accident prone stretch.
Accident Rate ( i ) Total no. of accident in year on the stretch i Total traffic in year on the stretch i
6.Quantum of accident method In the quantum of accident method consequent three years of data is considered for analysis
W
i 1
* Ai
WSI( j )
WST( j ) * K PCU( j )
Based on the values of WSI, mean, standard deviation, the accident prone locations are identified and divided into three types. Accident prone locations of First Order WSI = Mean + 2SD Accident prone locations of Second Order Mean + 2SD > WSI Mean + 1.5 SD Accident prone locations of Third Order Mean + 1.5 SD > WSI Mean + SD
Consistency Consistency means how frequently the accidents are taking place at the location. Tendency Tendency means whether the numbers of accidents at the location are increasing regularly or it is consistent or reduced. Level Level means that the magnitude of accidents in quantitative terms.
Sr.No.
Accident Scenario
Number of accidents > 3 every year
Points
40
20
10 0 20 15
No increase in 3 years
No accident Number of accidents in 3 years are 6 or >6
10
0 40 30 20 0
Number of accidents in 3 years are between 3 & 5 Number of accidents in 3 years are between 1 & 2 No accident in 3 years
Multi factor approach assigns weight to different accident reflecting severity, type of road user involved and accident cost information.
This has been mainly recommended for identifying black spots with higher pedestrian accidents.
ENGINEERING METHODS
Drivers characteristics or response at the location is taken into consideration. The bio-medical techniques are difficult to be used by organizations lacking in the necessary expertise for carrying out field studies
Based on the result of the safety evaluation by a group of drivers, traffic engineers, experts of traffic safety and others. Multi dimensional perceptual study of road safety is the ultimate aim of the subjective assessment methods.
This method is used for identification of high crash locations. The EB method controls the randomness of crash data by using an estimate of the long-term mean number of crashes at a location. It is used for predicting crashes in the future and then ranking based on the predicted number of crashes.
Main disadvantage
Cross-section Sight distance Horizontal alignment Vertical alignment Drainage Medians and barriers Curbs ,Shoulders and Grading
CROSS SECTION
Relative accident rate with roadway width
Road way width, m 4.5 5 5.5 6 6.5 7 7.5 8 9
2.2
1.7
1.4
1.3
1.1
1.05
1.0
0.9
0.8
HORIZONTAL ALIGNMENT
Running off the road and hitting an object Lost control and Rolled over
Driver entering the bend at too high a speed Driver was paying insufficient attention or because he misjudged the severity of the bend.
Accident rate per million vehicle kilometers with radii of horizontal curves
Radius of curve, m Accident rate 50 3.2 150 2.8 200 1.6 250 0.9 500 0.8 1000 0.4
VERTICAL ALIGNMENT
Natural topography Available right-of-way Utilities Roadside development Natural and man-made drainage patterns
2
1
3
1.5
4
1.75
5
2.5
7
3
8
4
SHOULDERS
2.2
1.7
1.4
1.2
1.1
1.0
PAST REVIEWS
geometry and crash risk differs between regions and that the
parameters characterise. that influence crash risk are difficult to
Davies (2000) looked at the relationship between road geometry and crash risk for all vehicle types. That study found significant effects due to the horizontal average curvature, difference between maximum and minimum horizontal
curvature, and the minimum advisory speed. Small effects were also found for the gradient, direction, sealed carriageway width and annual average daily travel. There are possibly effects associated with surface age, surface type, wet or dry surface, and accident type. There were no significant effects due to cross section slope or vertical curvature.
crashes on the State Highway network in New Zealand. They estimated that heavy vehicle crash risk could be reduced by 8% per metre of widening for small increases in road width. This result is backed up by McLean (1997) who estimated a reduction in crash rate of 2% to 2.5% per 0.25 metres of widening. However, there were other predictors such as AADT that had a much stronger relationship with crash rate. These
METHODOLOGY
Preparation of accident data format Accident data Collection from secondary sources
Tabulation and General Analysis of Accident Data Selection of Black spot Identification Method
Analysis and Identification of Black spots Selection of Major Blackspots Collection of Geometric features at selected Blackspot
Tabulation and General analysis of Geometric details Model Development for the Determining the Relation between Geometric Features and Safety
SHORTEST POSSIBLE RANGE GREATEST POSSIBLE RANGE MEASURING TIME Prism mode: <2sec
1.5 m 3000m
On Rajiv Rahadari, 42 Km covered in Rangareddy, 81 Km covered in Medak and 101 Km covered in Karimnagar
The
study
on
Rajiv
Rahadari
(passing
through
the
The secondary data was obtained from the concerned police stations for the above mentioned districts.
Accident data analysis was carried out for the period of 2002-
2006
The accident prone locations were identified using Crash density method ,Crash Frequency method.
1.81 3.13
BLACKSPOTS IDENTIFIED
Police Station
L.M.D.Colony Station Timmapur Siddipet urban Koheda Shameerpet Siddipet rural Bollarum Kukunurpally Gajwel Bejjanki Knr rural
No of Accidents
231 39 44 175 82 67 182 259 84 109
Average
46.2 7.8 8.8 35 16.4 13.4 36.4 51.8 16.8 21.8
Length of stretch(km)
10 2 4 20 12 10 28 40 14 30
Crash Density
4.62
3.90
2.20 1.75 1.37 1.34 1.30 1.30 1.20 0.73
Alwal
14
2.8
12
0.23
From the crash density method of analysis Average crash frequency = 29.22
BLACKSPOTS IDENTIFIED
S.No
1
Blackspot
Gajwel L.M.D.Colony Station Timmapur Kukunurpally Shameerpet Karimnagar rural Bejjanki Siddipet rural Bollarum Koheda Siddipet urban Alwal
Crash frequency
64.75
57.75
45.50 43.75 27.25 21.00 20.50 16.75 11.00 9.75 3.50
2
3 4 5 6 7 8 9 10 11
blackspot location
The blackspot locations under LMD colony station are given in table.
The total length of stretch considered (Alugunur to Timmapur) for analysis is 6.43km.
BLACK SPOT
ALGUNOOR EENADU OFFICE LMD COLONY MAHATMA NAGAR ST ANTHONY SCHOOL
CRASH RATE
16 0.25 9 0.25 0.25
THIMMAPUR
.xls
CR =
-11.99 + 18.8 614(CM) + 6.01(USW) - 15.0266(PSW) 0.0153(RAD) - 6.5864(SE) - 0.0908(HSD)+7.4118(TR) 0.0213(VSD) R2 = 0.835
99% significance value 1.884 1.554 1.628 1.615 0.818 2.427 0.819 6.87
Variable
CM USW PSW RAD SE HSD TR VSD
T-test value
-1.74 -1.32 -1.4 1.38 -0.28 2.38 -0.38 6.61
LOCATION
ALGUNOOR EENADU OFFICE LMD COLONY MAHATMA NAGAR ST ANTHONY SCHOOL THIMMAPUR
3 6.17 1.00
2 21.20 3.43
1 36.22 5.87
Radius
Crash Rate Relative Accident Rate
1000
0.87 1
500
8.52 9.75
250
12.35 14.12
200
13.11 15.00
150
13.88 15.87
100
14.64 16.75
50
15.41 17.62
Super Elevation
Crash Rate Relative Accident Rate
7 4.82 1
6 11.41 2.37
5 17.99 3.73
4 24.58 5.10
3 31.17 6.46
2 37.75 7.83
1 44.34 9.20
200 3.15 1
75 14.50 4.61
50 16.77 5.33
8 31.81 1
7 24.49 0.77
6 17.08 0.54
5 9.67 0.30
4 2.26 0.07
50 14.79 1.40
CONCLUSIONS
Along the horizontal curves, radius and sight distances are insufficient for the vehicles which are moving at greater than the design speed which is 60kmph.
Most of the accidents were occurred near the junction where there is no proper sight distance for the vehicles coming from the minor road to merge or diverge from major road. This problem can be overcome by providing the service roads for the minor road vehicles so that they can merge or diverge into major road traffic.
The number of culverts along the section are more. At these locations
the carriage way width was drastically decreased and because of improper signboards the drivers are unable to judge the situation.
continued
LIMITATIONS OF STUDY
If the accident data is precise i.e. time and date of accident and gap between two accidents occurred in a section is known then there will be a possibility of fitting a better binomial or Poisson distribution which is not possible with the present available data.
The model developed can be used for predicting the future crash rate value, but accident rate does not solely depend on geometric features but also the number of cross details, number of culverts and traffic regulations maintained along road.
traffic volume.
Accident cost analysis can be carried out to find the appropriate balance between road safety benefits and costs.
Road safety audit can be done to get the further details like encroachments, position of signboards, etc., and other improvements can be stated by auditing along the road.
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