Applications of the Safety Level of Service Method in Safety Evaluations of Intersections at the Design Stage

Highway intersections experience high numbers of traffic accidents. There are two traditional evaluation methods for intersection safety analysis. The direct assessment method is based on statistics of traffic accidents and the indirect method is based on the traffic conflict technique. While both methods rely on traffic data collected after intersections are built, this paper presents a method which evaluates the intersection safety during the intersection design stage. In order to develop the model, the influences of model objective factors are analyzed. Based on the analysis results, a main model is developed based on the conflict points and traffic flow, and a correctional model is established according to geometry property and traffic signs. The main model and correctional model are eventually combined for the purpose of real world applications. In the Jiangsu Province Coastal Highway Project, the safety level of service is divided into 4 levels according to the calculated values of the 40 intersections. A safety evaluation and optimization scheme is presented accordingly. The method is proved to be feasible in evaluating intersection safety on the design stage by comparing the calculated values before and after intersections improvement.