Analysis of conflict factors between pedestrians and right-turning vehicles at signalized intersections

Due to the fact that there is no protected signal phase for right turns at most signalized intersections, the conflict between pedestrians and right-turning vehicles is one of the most common conflict types for pedestrians. A pedestrian safety analysis of the common right-turn mode at four-phase signalized intersections is presented. Relative risk is used as a measure of the effect of behaviors. The analysis mainly includes five pedestrian factors that affect the conflict process between pedestrians and right-turning vehicles. Pedestrians tend to have a higher risk of being involved in conflicts in the following six situations: crossing with others, running over the crossing, entering the intersection, being near the exit lane, crossing in the middle or at the end of a green light when the right-turn lane is shared, crossing at the beginning of a green light or red period when the right-turn lane is exclusive. It is easier for pedestrians to get priority when crossing the street in the following situations: running over a crossing, entering the intersection, being near the entrance lane, and not using the crosswalk. However, pedestrians are more inclined to yield to right-turning vehicles when pedestrians are crossing in the middle of the green light time. Some measures to alleviate the conflict are put forward according to the conclusion. Video observations also indicate that a clear pedestrian waiting area must be marked for both pedestrian safety and right-turning vehicle efficiency at major flat intersections, particularly when the arms cover the lateral dividing strips.

Optimal allocation model of signalized intersections with dynamic use of exit lanes for left turn

In order to improve the operational efficiency of heavy left-turn demand intersections,an optimal allocation model of an intersection with dynamic use of exit lanes for left turns(EFL)is proposed.The constraints of setting EFL are analyzed,including the number and length of reverse variable lanes,flow direction constraints,and signal constraints,etc.The constraints and control variables are combined in a unified framework for simultaneous optimization.The objective functions are defined as the average delay and left-turn capacity of an intersection.The model is solved by a non-dominated genetic algorithm(NSGA-Ⅱ).The results show that after the optimal allocation of EFL,the average vehicle delays of the intersection can be reduced by 14.9%and left-turn capacity can be increased by 19.3%.The effectiveness of the optimal allocation model of EFL is demonstrated.