The Effect of Shoulder on Safety of Highways in Horizontal Curves: With Focus on Roll Angle

Abstract

Analysis of crash rates in the world reveals a number of factors including road geometry and human behavior which should be scrutinized. In fact, many studies have been conducted on how to decrease crash rates that are related to the relationship between human behavior and road geometry. In this research, 324 scenarios were evaluated to simulate vehicle dynamics with the use of Carsim and Trucksim simulation software. To be more specific, the impacts of shoulder width, slope of shoulder and material of shoulder surface on the enhancement of safety based on driver behavior and road geometry were studied, through the use of vehicle dynamic simulation. In the study, based on the position of vehicles in horizontal curves in various types of shoulders, models were achieved for the roll angle of vehicles. The research included: 1-3D modeling by using simulation software, 2- Evaluating roll angle changes in different types of vehicle locations on shoulders versus speed changes, and 3- Presenting multiple linear regression models to connect the variables by statistical programs. Results indicate that shoulder type (width, material and cross slope) influences the safety considering the roll angle of the vehicle. This influence depends on dynamic and geometric characteristics and type of the vehicle.