一种环形交叉口“左转两步”信号控制的新方法

A New Method of Two Step Left-Turn Signal Control for Roundabouts

为避免环形交叉口各车流发生冲突,首先以“左转两步”控制原理及“双环”相位相序为基础,分析了不同相位环道信号灯的运行关系。其次提出了二次左转车辆储存时长概念,并设计了基于左转车流储存时长的环道周期计算方法(取环道不同相位实际左转车流最大储存时长作为环道周期)。在相位衔接上,结合实际左转流量给出了左转车流潜在冲突判断,对进口道左转绿灯启亮时间进行了优化。同时根据二次左转车辆运行特征和左转流量给出了环道绿灯优化时长。最后以车均延误、平均最大排队长度为指标设计了总流量增减试验、左转比例增减试验、不同环形交叉口直径试验,验证不同配时方法的适用性。总流量增减试验表明,总流量约为2200~6500veh/h时,新方法车均延误相较于Yang方法减少12%,相较于Cakici方法减少20%。左转比例增减试验表明,新方法适用于左转车流比例小于35%;Yang方法适用于左转车流比例35%~50%;不同环形交叉口直径试验表明,Cakici方法适用于直径不小于80m的环形交叉口。

In order to avoid conflicts among traffic flows at roundabouts,the operation relationship of ring road signal lights with dfferent phases is analyzed based on the control principle of two steps left-turn and the phase scheme of dual-ring,and the concept of the storage time length of the second left-turn vehicles is proposed.A calculation method for the cycle length of the circulating lane based on the storage time length of the left-turn traffic flow is designed(taking the maximum storage time length of the actual left-turn traffic flow with different phases of the ring road as the cycle).In terms of phase connection,the potential conflict judgment of left-turn traffic flow is given in combination with the actual left-turn traffic flow,and the green light on time of left-turn at the entrance is optimized.According to the running characteristics of the second lef-turn vehicles and the left-turn flow,the optimal green light duration of the ring road is given.Finally,with the average delay of vehicles and the average maximum queue length at intersections as indicators,the experiments of total flow increase and decrease,left-turn proportion increase and decrease and different roundabouts diameter are designed to verify the applicability of different timing methods.The experiments of changing the whole traffic volume show that when the total flow is about 2200-6500 veh/h,the average vehicle delay of the new method is about 12%less than that of Yang method and about 20%less than that of Cakici method.The experiments of changing the left-turn proportion show that the new method is suitable for left-turn traffic flow with a ratio of less than 35%.Yang method is applicable to left-turn traffic flow with a proportion of about 35%-50%,and the experiments on the diameters of different roundabouts show that the Cakici method is applicable to those with diameters no less than 80 m.