Investigating Factors Affecting the Occurrence And Severity of Rear End Crash at Signalized and UN signalized Intersections: A case Study of Kirkos Sub-City, Addis Ababa, Ethiopia.

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.