Abstract:

The vehicle flow under a protected left- turn phase is commonly affected by pedestrians. This paper investigates the average operating speed at the saturation flow rate with and without pedestrian traffic, and evaluates the effect of pedestrians, using the method of significant analysis. The influence factors contain the position (inside or outside of left-turn vehicle’s trajectory) and the number of pedestrian and the distance between the vehicle and pedestrians. The degree of pedestrian-vehicle impact is defined in four levels and the speed profile for the queuing vehicles in different impact levels is fitted by curve fitting software. The results show that saturation flow speed is mainly affected by the position of pedestrian (inside or outside of left-turn vehicle’s trajectory), and the distance, while the number of pedestrians is not an influence factor. The effect on the left- turn saturation flow by both sides of pedestrians is same to the effect by pedestrians on one serious side. The speed-time profile indicates an“S”shape from queuing vehicles start to reach the stable saturation flow, the vehicles need more time to reach the saturation flow when affected by the pedestrians, and the saturation speed is lower. However, the“S”shape of the speed- time profile is not affected. These findings may help lay a foundation for a better traffic management.

Key words: urban traffic；impact of pedestrians；significant analysis；exclusive left- turn lane；speed of saturate flow, speed profile

摘要：

中国信号交叉口中，机非干扰现象十分普遍.本文通过实际调查，以无行人影响的左转饱和车流为基础，通过显著分析方法，量化了行人位置（转弯车流内、外侧与距离）、人数对专用左转车流车速的影响，并根据严重程度将影响划分为4 个等级，同时拟合了各级影响下排队车辆起步后的速度时间变化曲线.研究结果表明：（1）行人距车流距离是显著影响因素，而行人人数不是；（2）车流两侧同时有行人对饱和车流造成的影响，与其中较严重的单侧行人影响情况相同；（3）排队车辆在加速过程中的速度变化曲线呈“S” 型，行人对车流影响越严重，车流加速到饱和流所需时间越长，饱和流车速越低，但不影响速度—时间曲线线型——“S”型.这些结论可为科学的交通管理奠定基础.

关键词: 城市交通, 行人影响, 显著分析, 专用左转车道, 饱和流车速, 速度曲线