易军伟

       随着机动化、城镇化进程的加快和城市交通拥挤带来的问题日益加剧，交通拥挤成为国内外大中城市面临的重要问题。交叉口作为城市交通系统的咽喉，其通行效率往往直接关系到整个区域的交通系统运行状况，也是最容易发生拥挤的地方，对交叉口拥挤的信号控制因此成了交通控制系统的重点。交通领域的学者对交叉口信号控制的研究从单点配时优化发展到线控和面控等区域化的智能控制系统，解决交叉口拥挤问题的角度也从配时参数优化发展到车辆行驶路径诱导等宏观层面的控制管理。但是，由于受交叉口通行能力的限制，交叉口拥挤依然是交通控制系统中的难点和亟待解决的问题。

       本文在国内外研究现状的基础上，对信号交叉口拥挤判定方法和不同拥挤状况下的单点信号控制策略进行了研究。首先，对信号交叉口交通状态指标参数进行了分析，并结合实地调查数据，通过对上海市长宁路-江苏北路交叉口车流状况进行分析得到了交叉口车流运行特性，认为可以采用交通量、延误、排队长度和车头时距四个指标来建立信号交叉口拥挤综合评价指标——拥挤指数。为了避免这四个指标相互之间内在关系对综合评价指标的影响，采用主成分分析法建立拥挤指数的计算方法，消除了各指标间的多重共线性，通过对比临界值即可判定交叉口交通是否处于拥挤状态。然后对现有的信号控制策略进行了分类对比分析，提出了在全拥挤和部分拥挤两种不同的拥挤交叉口适用的信号控制策略，并采用VISSIM交通仿真软件进行了仿真分析，仿真运行结果表明在全拥挤交叉口采用变相位相序信号控制策略和在部分拥挤交叉口采用变车道信号控制策略具有一定的效果。

关键词：城市交通，交叉口拥挤，信号控制策略，交通仿真

    With the speeding up of motorization and urbanization and the problem caused by the traffic congestion growing in intensity, the traffic congestion is becoming serious issue of many cities at home and abroad. As the throat of the urban transportation system, the efficiency of the intersection always affect the state of the whole transportation system, and the intersection congestion indeed occurs easily, therefore the signal control of intersection become a very important part of the urban traffic control system. The research emphasis of transportation scholars developed from the optimization of the signal timing parameters of single intersection to the proper intelligent control system for all intersections in large area, the angle of view for solving traffic congestion in intersection transformed from optimizing the signal timing parameters into driving route guidance and some macro-level control and management measures. But because of the restraint of capacity in intersection, solving the traffic congestion in urban intersection is still a difficult and pressing problem.

    Based on the present research done by scholars both at home and abroad, the method of judging intersection congestion and the proper single intersection signal control strategy for different types of congestion are studied. Firstly, the traffic status indicators of the signal control intersection are analyzed, and according to the on-the-spot investigation, obtained some features of the traffic flow by analyzing the traffic status data collected at the junction of Changning Road and North Jiangsu Road in Shanghai, and the intersection congestion integrated assessment index created by four basic indicators(traffic volume, average delay, queue length and average time headway)--congestion index is proposed. To avoid the internal relation of the four indicators affecting directly on the congestion index, using the principal component analysis (PCA) method to analyze the four indicators and model the congestion index, and by comparing the threshold limit value and the actual value of the congestion index of the real time traffic flow, whether the intersection is congested can be confirmed. Then, the present single signal control strategies are compared and analyzed, and the proper signal control strategies for all congested intersection and partly congested intersection are put forward. And finally via the VISSIM traffic simulation, the effect of the different strategies for different types of congested intersection is tested, the result of the simulation shows that the signal phase sequence changeable strategies in all congested intersection and the lane direction changeable strategies in part congested both have certain effects.

Key Words: urban transportation, intersection congestion, signal control strategy, traffic simulation