Studying the effect of spiral curves and intersection angle on the accident rates on two-lane rural highways in Iran

Abstract

Safety on highways is one of the most important subjects in Transportation Engineering. The increasing rate of vehicles and the needs to design or geometrically modify the highways has been emphasized in the safe-design of roadways more than before. Between the constructive components of the highway, due to the increasing occurrences of accidents the horizontal curves are of great importance. The US Ministry of Highway and Transportation introduced the IHSDM software, with variant capabilities to predict accidents. In this research, five types of curves (simple circle curve and clothoid-circle-clothoid) at different intersection angles were designed, and based on the standard specifications on each curve accident rates were predicted by using IHSDM. The results have been compared with each other. Finally, by processing the curves of accident rates versus curve types and intersection angle, and comparing them with each other, the necessity of using spiral curves in the highway design is emphasized.