Study on Accident Risk considering Traffic States and Road Geometry in Intercity Expressways

Abstract

This research aims to investigate the relationships between the accident risk and various factors such as traffic states, road geometries and weather conditions. Abundant study has been conducted to identify the accident risk factors for inner city highways. However, few has been reported for intercity expressways. This research first defines the traffic environment categories. The category considers traffic states, horizontal and vertical alignment, tunnel and precipitation. In defining the traffic states, this research proposes the method to identify the four states: free flow, capacity flow, congestion and mixed-state flow. Then, the accident risk is calculated for each traffic environment category to reveal the effect of the factors on accident risk. The results identified that the risk of sideswipe accident in mixed traffic state is higher in multiple lane sections. The study also revealed that the risk of crash accident is higher in the entrance of tunnels. Future research needs include the development of accident risk estimation model based on the findings from this study.