Signal-control Method for a New Left-turn Waiting Area at Intersections

In view of the low efficiency of traffic flow and serious traffic conflicts between through and left-turn vehicles during the permitted-phase operation at signalized intersections, a new method for setting the left-turn waiting area in the permitted phase was proposed. The corresponding signal phase scheme was designed, and traffic conflicts before and after setting the left-turn waiting area were analyzed. In this study, a delay model was established after setting a new left-turn waiting area, the optimized model of the signal control parameters of the improved intersection was established with the minimum average delay of vehicles as the optimization objective, and the solution algorithm was developed. Taking the intersection of Rongjiang Road and the sixth Qunli Avenue in Harbin, China, as an example, the VISSIM simulation shows that, although the method proposed in this study is not suitable to reduce the delay and the stop rate of left-turning vehicles on the side road, the total delay of vehicles on the side road is reduced and the delay on the main road especially decreases. This highlights that the method proposed hereby is feasible and effective. Furthermore, the influence of traffic volume and the proportion of left-turn vehicles before and after setting the left-turn waiting area, as well as the effect of the left-turn waiting area on the delay on the side road were analyzed. The results show that when the capacity of the left-turn waiting area in each direction is fixed, more left-turn vehicles arrive in red time, the higher the critical point of hourly traffic volume on the side road associated with the method proposed in this study, and with the increase in the hourly traffic volume on the side road, the critical left-turn ratio of the proposed method decreases. In the same traffic conditions, the greater the capacity of the left-turn waiting area in each direction is, the smaller the delay of vehicles, that is, the more effective the method proposed herein is. Therefore, the proposed method improves the traffic safety and efficiency at signalized intersections, including in the permitted phase. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.