许可相位下左转车道存储段长度计算

Calculation of storage lengths for left-turn lanes with permitted phases

以左转交通量、周期长度、左转绿灯时间、对向交通量为变量,运用交通流理论和排队论,从满足左转排队车辆停车需求的角度,对信号交叉口进口道设置左转许可相位和一条左转专用车道时的左转车道存储段长度展开研究。基于M/M/1排队系统,建立许可相位下单条左转车道存储段长度计算的理论模型。在此基础上,讨论模型的适用条件和实用性,分析存储段长度随饱和度、左转交通量的变化规律,综合考虑空间几何条件、服务质量、经济性能,指出排队车辆数不宜超过20辆,如置信概率为95%,则实用饱和度区间为[0,0.8]。讨论置信概率、设计交通量及单位车辆停放长度等参数的取值方法。对典型情况计算、分析,提出极限交通量、极限排队长度、临界交通量、临界排队长度两组便于工程应用的概念,并绘制图表。制定应用图表确定存储段长度的流程;讨论设计快速校核表的制定和应用。该研究为交叉口采用左转许可相位且进口道仅设置一条左转车道的存储段长度确定提供依据,也可作为左转专用相位的设置依据。

The storage length of left-turn lane for signalized intersection approach with permitted phase and only one left- turn lane is studied using traffic flow theory and queuing theory. The storage length is supposed to meet the requirement of left-turn vehicle queuing. The main variables are left-turn volume, cycle length, left-turn green time and opposing traffic volume. A theoretical modal for calculating the storage length of single left-turn lane with permitted phase is established with M/M/1 queuing system. The applicable conditions are discussed. Variations of storage length with degree of saturation and left-turn volume are analyzed, and the thresholds for queue length, degree of saturation, etc. are proposed with overall consideration of geometric condition, service quality and economic performance. It is indicated that the number of queuing vehicles is not more than 20, and the practical saturation interval is [0, 0.8 ] for a 95% probability. Methods for determining three key parameters are discussed, with the first being the confidence probability, the second the design traffic volume, and the third the queuing headway. Calculations and analyses are conducted for general conditions. Two sets of concepts are proposed in order to facilitate application, which include the limiting traffic volume, queue length, critical traffic volume and critical queue length. The development and application of design quick check tables are discussed. The results were charted and the processes of determining the storage length are developed. The development may serve as calculation guidelines for single left-turn lane with permitted phase at signalized intersection approach, as well as for protected left-turn phases.