Quasi-optimal feedback control for a system of oversaturated intersections

Oversaturated intersection control is a long-standing problem in traffic science and engineering. The problem becomes even harder when we consider a system of oversaturated intersections. Most of the research works in this area are off-line studies that require fully knowledge of origin–destination demand, which would be difficult to obtain in reality. Although several on-line feedback control methods are proposed, they only aim at preventing queue spillover, not able to minimize vehicular delay time. Moreover, these on-line control strategies are not theoretically evaluated how optimal (or sub-optimal) they are. We propose in this paper a quasi-optimal decentralized QUEUE-based feedback (abbreviated as QUEUE) control strategy for a system of oversaturated intersections. The QUEUE strategy is applied cycle-by-cycle based on measurement of current queue sizes, but its overall result is able to approximate the optimal one derived from off-line studies. Details of the feedback control laws for upstream and downstream intersections, in the queueing period and the queue dissipation period, are discussed. Superior to the existing feedback control strategies, the upper bounds of sub-optimality of the QUEUE strategy generating from demand fluctuation and coupling of intersections are specified quantitatively. It is also theoretically proved that the queue measurement error or demand estimation error would not be amplified by the QUEUE strategy. Numerical examples show that the QUEUE strategy performs very well and is robust to errors.     

信号交叉口车辆到达规律分析

信号交叉口是中断车流的重要结点,其车流到达规律的准确描述是交叉口信号控制设计的重要影响因素。信号交叉口车流的到达规律是随机且多样的,并服从一定的统计规律。本文对信号交叉口到达车流的到达时间间隔的统计分析进行拟合,发现信号交叉口车流的到达规律与其变异系数的平方存在耦合关联,并得出结论如下:对数正态分布的拟合范围为0.8874~0.9904,平均拟合度高达0.9489,拟合效果最佳;伽马分布的拟合度范围为0.5352~0.9449,平均的拟合度为0.8056,拟合效果次之;威布尔分布拟合度在0.1997~0.8991之间,总体波动较大,平均的拟合度为0.616;正态分布拟合范围为0.2585~0.6671,平均拟合度为0.6252;指数分布拟合度范围是0.0365~0.4077,平均拟合度是0.2317,拟合效果最差。     

含邻域交的Hamilton及Hamilton连通图

对任意一对不相邻的顶点u和v,α(u,v)表示图G中含u,v的最大独立集的顶立数.通过讨论邻域交|N(u)∩N(v)|与α(u,v)的关系,本文得到了关于Hamilton及Hamilton连通图的新的充分条件,这些结果推广了现有的有关结果.     

Unconventional USC intersection corridors: evaluation of potential implementation in Doha,Qatar

Unconventional intersection designs have been recently proposed as a new approach to deal with heavy left turns at signalized intersections. One of these unconventional schemes, the Upstream Signalized Crossover (USC) intersection, was shown to significantly reduce average vehicle delays; particularly when the volumes entering the intersection are relatively high. The Ministry of Public Works of Qatar is considering the implementation of the USC intersection on three signalized intersections along a major urban corridor in Doha. This paper investigates the potential improvements associated with the USC implementation. VISSIM was used to analyze the proposed USC intersections and the existing conventional intersections. Analyses were carried out for AM , Midday, and PM peak hours. The results showed that most of the travel time measurement sections experienced lower delays in the USC configuration for the three peak periods. As well, the total system delay, in hours, for the USC configuration was less than that of the conventional configuration by 19.4, 14.8, and 13.6% for the AM , Midday, and PM peaks, respectively. The average control delay for each single USC intersection was lower than its conventional counterpart by between 7.6 and 22.9%. Copyright © 2010 John Wiley & Sons, Ltd.     

信号交叉口直右共用车道通行能力研究

为了弥补国内对直右共用车道通行能力研究的不足,在现场观察的基础上,分析了其交通流运行特性.根据实测数据,运用统计学中的T检验法对不同转向车辆的饱和车头时距进行了分析,发现直右共用车道上直行车辆和右转车辆的饱和车头时距存在显著性差异;然后运用饱和流率修正理论和概率论方法,给出了适用于我国现阶段道路交通条件下直右共用车道通...     

信号控制交叉口行人过街交通组织与控制

行人既是信号控制交叉口交通事故中的弱者,也是交叉口秩序混乱和效率低下的根源之一.首先归纳了行人过街的典型心理和行为特征,分析了影响行人过街行为的诸多因素,包括行人自身特点、环境因素、交通因素、交叉口几何设计因素、信号控制因素、交通执法等.在此基础上提出了交叉口行人过街交通组织和控制的基本原则和基本方法.最后,选择典型交...     

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在北美交通早高峰与晚高峰期间,大量信号灯控制的交叉路口会处于过饱和状态.对于非饱和路口的信号设计,已经有许多行之有效的理论方法和信号控制策略可以使用;对于过饱和路口,当前却没有被广泛接受的信号控制模型可以直接采用.对于孤立的信号路口,实时有效的配时通常被认为是优化交通流的一个非常重要手段.基于这一原则,多种过饱和路口交通信号设计方案出现在以往的研究中。但是由于没有对这些方法进行过有效的综合评测,所以一直没有对各种设计方法优缺点的清晰描述.本文对两组经典饱和路口信号设计模型进行了详细的评测与比较,进而深入分析这些模型的特点与可用性.在研究中这两组模型的控制结果还与最新的信号设计软件TRANSYT 7F和Synchro给出的优化信号进行了比较.基于比较结果,最终得到用于过饱和路口信号设计的方法选择指南.     

基于公交优先通行的交叉口相位设计方法研究

交叉口公交优先是公交优先发展的一个重要措施,对缓解城市的交通压力和保证城市未来的可持续发展都具有重大意义。基于公交优先通行的相位设计是实施交叉口公交优先的有效措施之一,合理的相位设计将有助于求得最佳的公交优先信号控制方案。在交叉口相位设计过程中,不同流向的各股交通流的客流量可能会出现较大差异,但大多数信号设计对这种差异并不重视。本文在十字型信号控制交叉口典型相位设计基础上,对基于公交优先通行的相位设计方法进行了研究和探讨。实例分析表明:该方法在保持以pcu为单位的通行能力不变的条件下,提高以人为单位的通行能力,减少人均延误,充分体现以人为本的设计思想。     

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二次过街信号设计对于行人通过大型信号交叉口具有非常重要的作用。本文提出了行人信号相位与原机动车信号相位进行叠加组合的相位设计方法，并分析了在不同的机动车信号相位条件下和二次过街设置方式下的行人信号相位设计方案。为对可选信号相位设计方案进行比较，本文构建了各周期内各驻足区行人平均最长等待时间模型，并建立了评价行人二次过街信号相位设计方案的仿真分析模型。最后针对一个实际交叉口，应用提出的信号相位设计方法和仿真模型进行了分析研究。     

城市用地开发交通影响分析的案例解析

对三个用地开发项目交通影响分析的实际案例分别从不同的侧面进行了解析.案例A是对居住零售用地项目的交通影响分析,比较系统地演示了开展项目交通影响分析的主要步骤,包括分析方案的确定,现状交通条件、项目新增出行量及其交通影响的分析,以及交通影响消减措施的拟定和责任分担的计算.案例B针对在城市中心商业广场计划新建的一个超级市场项目,主要介绍了基于交通观测的相关系数模型法在项目出行分布预测中的应用过程.案例C则重点阐述了运用交通规划模型来分析大型区域性商业开发区的交通影响.最后对几个基本技术问题进行了讨论.