Analysis of the Contributory Factors to Accidents at Signalized Intersections using Generalized Estimating Equation with Negative Binomial Distribution

Abstract

Ensuring safety on roadways and controlling conflicting and merging streams of traffic at signalized intersections has become a major concern for transportation engineers and road users globally and locally. Many factors contribute to accident occurrence at road segments and intersections with driver behavior being the major contributor.  Other factors include those related to the vehicle and the road. The primary aim of this study is to understand the impact of different factors causing traffic accidents at signalized intersections.  It also include developing a descriptive study of traffic accident data to show the variation with different factors at both intersections and roadway segments. To achieve this objectives, 22 signalized intersections and all roadways in Duhok city/Iraq were selected.  Assessing the effects of geometric characteristics and driver behavior on safety performance of the sites have been achieved through observations of trends from graphs and use of appropriate advanced statistical analysis such as Generalized Estimating Equation (GEE) with NB distribution and log link function.  The results show that approach width, driver inattention, red light running and surface moisture condition are the significant contributors to accident occurrence. The study results highlight the importance of driver education, police enforcement and appropriate geometric design of intersections to the reduction of accident occurrence.