一种改进的移位左转车道信号控制方法及其效用分析

针对交叉口传统移位左转交通组织存在的交通冲突与通行效率问题,提出了一种改进的移位左转车道设置方法,并分析改进前、后的交通冲突状况.综合考虑行人与非机动车的过街需求,分析路段左转信号与交叉口主信号之间的协调控制关系,设计改进的移位左转交叉口相位方案,建立移位左转交叉口设计要点计算模型,包括移位左转车道长度、路段左转变道段长度、路段左转车储存段长度.假设车辆到达服从泊松分布,推导并建立改进的移位左转交叉口各相位的延误计算模型.以车均延误最小为目标,构建改进的移位左转交叉口信号控制参数优化模型,采用穷举法给出其求解算法.从左转交通量、移位左转车道长度、交叉方向右转车辆比重3个方面分析改进方法的适用条件,并借助VISSIM仿真,使用在哈尔滨市交叉口收集的数据验证改进方法的效用.研究结果表明:当移位左转车道长度为100 m左右时,该交通组织方式可以发挥最大效益;改进的移位左转交通组织较改进前交叉口车均延误下降了16.1%,验证了所提改进方法的有效性;当左转交通量小于400 pcu·h^-1,交叉方向右转交通量比重大于25%时,采用改进的移位左转方法,交叉口的通行效率改善更加显著.研究成果可为移位左转车道的设置及信号配时提供依据.

Signal Control and Utility Analysis of an Improved Displaced Left-turn Lane

To overcome the problem of traffic conflict and improve efficiency at Displaced Left-turn Intersections (DLI), this study proposes an improved setting method for displaced left-turn lanes at DLI and analyzes the traffic conflict before and after the improvement. Considering the demand of pedestrians and non-motorized vehicles crossing the street, the coordinated relationship between the left-turn signal at the road section and the intersection main signal was analyzed, and the phase scheme of the improved DLI was designed. The design calculation model of the displaced left-turn was established, including the displaced left-turn lane length, lane-changing length, and the length of the storage section of the left-turn vehicle. Assuming the vehicle arrival rate in each approach of the intersection is subjected to Poisson distribution, the delay model of each phase of the improved DLI was established. A signal control parameter optimization model for an improved DLI was constructed with the aim of minimum average delay, and the solution algorithm was defined by using the exhaustive method. The application conditions of the improved method with respect to three aspects, namely, left-turn traffic volume, length of the displaced left-turn lane, and right-turn proportion of cross direction, were analyzed, and the operational performance of the improved DLI was validated using the data collected at an intersection in Harbin using the VISSIM simulation. The results demonstrate that when the displaced left-turn lane length is about 100 m, the improved DLI can bring maximum benefit, and its' delay decrease 16.1% than improvement before. This indicates that the method proposed in this study is effective. Further analysis reveals that the efficiency of the improved method is more obvious when the left-turn traffic volume is less than 400 pcu·h^-1 and the proportion of the right-turns in shared through-right lane is more than 25%. This study provides a basis for the setting of the displaced left-turn lanes and signal plan.