Traffic Safety Evaluation and Development of a Traffic Safety Prediction For the Approaches of Signalized Intersection Model Using Surrogate Safety Measures (The Case of Bole Sub-city)
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Date
2024-06
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Addis Ababa University
Abstract
In developing countries like Ethiopia, particularly Addis Ababa, it has been noted that about 1,264
people have died from the year of July 2019 to June 2022 that was approximated 422 people die per
year. This emphasizing that Addis Ababa city has highly affected by traffic accident with a significant
loss of lives, serious injuries on individuals' well-being and property damage.
Traffic safety studies and analyses were traditionally conducted using reports on traffic crashes. The
drawbacks include failure to record the accident position, incompleteness, and underreporting of
crash data and additionally the drawback of the traditional approach is needed many crash data for
analysis, in order to draw any conclusions and take the appropriate corrective action. Thus, the
microscopic traffic simulation was chosen for the evaluation of traffic safety.
Eight signalized intersections with a combined total of 29 road approaches were selected and
Simulation of Urban Mobility software were used to model the existing situation. Primary and
secondary collected data are used as the input for the SUMO simulation to modify the default carfollowing
and lane changing model with actual real data.
Surrogate safety measures (TTC) for the selected study area were derived from Sumo output. TTC
has a bell-shaped distribution with some skewness and Weibull distribution function were used to
model the distribution of Time to collision distribution. After calculating the Weibull shape and scale
factor parameter the Weibull cumulative probability for Time to collision below 2.5second were
determined for all road approaches and used as dependent variables. Traffic safety evaluation was
carried based on Weibull cumulative distribution. The roads from Jacross to Gerji meberat-hayel
junction have the highest cumulative probability value of 0.779, or it has 77.9% chance of occurring
potential conflict, while the roads from Latica bakery to Salithmhiret intersection have the lowest
cumulative probability value of 0.164, or it has 16.4% chance of occurring potential conflict.
A multiple linear regression were used to model the dependent variable, (cumulative probably for
TTC below 2.5 seconds) and significant independent variables, (Traffic volume per lane and speed
deviation). The coefficients of number of vehicles per lane is positive 0.00076186 indicated that for
every increase of 100 vehicles per lane results the probability of the occurrence of potential conflict
increased by 0.076 or 7.6% and the coefficient of speed deviation is 0.50114603 for every increase of
speed deviation by 0.1 the probability of the occurrence of potential conflict increased by 0.0501 or
5.01%.
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Keywords
Traffic Safety Evaluation, of Signalized Intersection, Surrogate Safety Measures