Abstract:
To reduce injuries in rear end road crashes, better understanding is needed between
the relationship of rear end injury severity and risk factors. Factors such as driverrelated, time related, environment-related and intersection type related were
considered when developing statistical models to predict the effects of these factors
on the severity of rear end crashes at intersections.
The purpose of this study is to investigate factors affecting occurrence and severity of
rear end crash at signalized and unsignalized intersections in Kirkos Sub City, Addis
Ababa. The target population was considered all rear end accidents occurred in Addis
Ababa kirkos sub city signalized and unsignalized intersections, during the period
2015/16-20117/18 were included. The pivotal data necessary for the study was
collected from the daily Road Traffic Accident records format of the Kirkos Sub city
and Addis Ababa Police Commission. Descriptive stastics and ordred logit model is
developed to investigate and identifying significant contributing factors for rear-end
crash injury severities classified into four categories: pdo (no injury), slight injury,
severe injury, and fatality.
The results of the proportional odds model show that vehicle service age, day of crash
(thursday), light condition (day light), driver vehicle relationship (hired) and
educational level (preparatory school) were found to be significant predictors for
severity levels of rear end crash at signalized intersections. Similarly the time of rear
end crash, experience of drivers (less than one year ,1-2 year) and vehicle driver
relationship (owner) were found to be significant predictors for severity level of rear
end crash at unsignalized intersections.
Specifically the study showed that severity levels of rear end crash at signalized
intersections is more likely for vehicle service age (˂1 year, 1-2 year, 2-5 years, 5-10
year) than vehicle service age ˃ 10 years. Hired drivers are more likely to commit
fatal accident than others (reference group) and drivers whose educational level
preparatory school are less likely to commit severe outcome than those vehicles
whose educational level are above preparatory school (reference group) at signalized
intersections. Similary the study showed that severity levels of rear end crash at
unsignalized intersections (12 am-6 am, 6 am-12 pm, 12 pm-6 pm) is more likely for
time of rear end crash 6 pm-12 am (refernce group). Similary drivers whose driving
experience are (˂1 year, 1-2 year) are less likely to commit severe outcome than
those drivers whose driving experience above 10 years (reference category). Drivers
who drives their own vehicle and hired drivers are more likely to commit fatal
accident than drivers who drives others (reference group) at unsignalized
intersections. The developed methodology and estimation results provide insights
for developing effective countermeasures to reduce rear-end crash injury severities
and improve traffic system safety performance.
