Risk Evaluation Model of Unsignalized Intersection Based on Traffic Conflict Line Theory

In order to analyze unsignalized intersections safety performance objectively and systematically, given that the traditional traffic conflict research focuses on the two-vehicle conflict, a risk evaluation model based on “traffic flow conflict line” theory was developed. Firstly the characteristics of crossing, diverging and merging conflicts were analyzed. Due to different types of traffic conflicts caused different potential treats and collision severities, the research estimated the weighted values of crossing, merging and diverging conflicts through analyzing the leading vehicle conflict potential probability, collision severities and transmission length of traffic conflicts. Finally the research combined all results for establishing useful index of intersection safety called expected values of conflicts. Compared with the traditional method, the results show that the leading vehicle conflict probability model is closer to the real process of traffic conflicts based on the critical conflict distance. The model takes into account the speed, angle, acceleration and reaction time between two vehicles. Based on physics collision theory, analyzing the angle change, deceleration relation of the vehicle and the kinetic energy loss, three traffic conflicts weights were discussed when accident occurred (crossing conflict: diverging conflict: merging conflict = 12.7051:1:1). Based on the mathematical expectation method, the total equivalent expected conflict model was developed through analyzing the potential probability of conflict, traffic volume and vehicle position, so this model can more accurately describe the actual traffic flow conflict behavior.