实时信息交换技术在地铁清分系统中的研究与实现

基于TCP/IP协议,从逻辑架构、处理流程、技术特点、数据结构定义、模块功能、业务逻辑和数据库的实现等方面,对采用多层体系结构的实时信息交换系统作了详细的阐述。给出了它作为轨道交通清分系统的重要子系统的一个应用实例。实践表明,该技术的实际应用提高了整个清分系统的可靠性、可扩展性、可管理性和安全性。     

高速公路出口匝道交通安全评价方法研究

在大量现场踏勘的基础上,文章明确了出!zr匝道的交通安全评价方法和流程,从几何安全、设施安全、交通管理与控制3个方面。构建了出口匝道的交通安全评价指标体系,采用专家问卷调查的方法。确定了各项指标的相对权重系数。给出了打分数据的处理方法。采用累积频率曲线分析的方法,选择安全性较好一组15％位累积频率对应的数值作为出口匝道...     

Queue discharge patterns at signalized intersections with green signal countdown device and long cycle length

Two apparent features that prevail at signalized intersections in China are green signal countdown device and long cycle lengths. The objective of this study is to investigate the impacts of green signal countdown device and long cycle length on queue discharge patterns and to discuss its implications on capacity estimation in the context of China's traffic. At five typical large intersections in Shanghai and Tianjin, 11 through lanes were observed, and 9251 saturation headways were obtained as valid samples. Statistical analyses indicate that the discharge process of queuing vehicles can be divided into three distinct stages according to the discharge flow rate: a start‐up stage, a steady stage, and a rush stage. The average time for queuing vehicles to reach a stationary saturation flow rate, that is, the start‐up stage, was found to be approximately 20–30 seconds; the rush stage usually occurs during the phase transition period. The finding is contrary to the conventional assumption that the discharge rate reaches a maximum value after the fourth vehicle is discharged and then remains constant during the green time until the queue is completely dissolved. The capacity estimation errors that might arise from the conventional methods are discussed through a comparative study and a sensitivity analysis that are based on the identified queue discharge patterns. In addition, a piecewise linear regression method was proposed in order to reduce such errors. The proposed method can be used for capacity estimation at signalized intersections with the identified queue discharge patterns. Copyright © 2017 John Wiley & Sons, Ltd.     

Consistency of Input-Output Model and Shockwave Analysis in Queue and Delay Estimations

This paper investigates the consistency between the simple input-output model and the shockwave analysis method as applied to traffic bottleneck problems. Mathematical derivations considering changes in arriving demand and discharge rate have shown that these models are consistent in queue and delay estimations, as both methods produce identical results at anytime during the congestion propagation and dissipation processes. Earlier findings on the inconsistency of these two methods are attributed to the lack of consideration of the baseline factor, which is dependent on the level of background traffic. Numerical examples are presented to illustrate the importance of the baseline factor, to ensure consistency regardless of the use of different flow-density relationships.     

道路交通事故的影响范围算法

为了及时有效地采取交通流诱导措施以减少交通事故对路网的影响,对交通事故影响范围的确定方法进行研究。首先分析了路段和交叉口两种类型交通事故对路网的影响。以交通波理论为基础进行交通事故影响范围算法分析,将影响范围分成交通事故处理和交通事故持续影响两个时间段,对每一段的交通波速度、排队长度等给出相应的计算方法和步骤,最终得到确定影响范围的流程图。以虚拟路网进行算例分析,证明了算法的可行性和实用性。     

New Approach to Measuring Traffic Queue at Intersections

To measure the length of traffic queue, a vehicle motion model at intersections was built, and based on it the effective traffic queue was defined. Color images segmentation and frame differencing technique were used to detect the foreground and the moving vehicles by detecting regions of the images, and then measure the length of effective traffic queue. By processing the image sequence acquired at certain intersection, the results prove that it is able to work out the traffic queue effectively by using the two techniques.     

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信号交叉口是城市交通系统的重要组成部分,制定合理的交叉口拥堵和安全治理方案尤为重要.交叉口扩容是缓解交叉口拥堵最直接有效的措施,但是传统的扩容方案（如增加车道,禁止左转和立体交叉等）,可能并不能达到预期的效果.由于上游的扩容,下游交叉口的交通状况可能会急剧恶化,导致更长的车辆排队,这些排队车辆可能蔓延至上游交叉口,引起堵塞.此情形在车流量大、交叉口之间距离小和信号灯周期长的情况下表现尤为显著.本文提出了一个简单、准确且实用的方法,用于判定这种下游排队蔓延现象的发生及其种类（循环性或持续性）,并且评估这种排队蔓延对上游信号交叉口通行能力的影响.此方法基于最新的美国交通运输署的高速公路通行能力手册.本文还介绍了该方法相应的计算程序的开发和运用,并给出运用实例.     

定点停靠公交的服务效率与停靠能力研究

在多线路公交站,为规范乘车秩序,实现乘客排队候乘车,需要公交车在公交站内各指定位置进行停靠,即定点停靠。但是现实中定点停靠措施使公交车出现排队拥堵的频率大为增加。鉴于此,首先根据排队论建立了定点停靠公交站排队模型（c_M／M／1型）与自由停靠公交站排队模型（M／M／c型）,通过服务指标的比较探讨出现此现象的理论原因;其次,运用排队概率方法建立公交站合理停车位数量的计算模型,并在综合考虑公交车到达频率、平均停靠时间以及可忍受排队概率等因素的基础上．计算两种类型公交车站的合理停车位数量。研究得出,在公交车平均到达率与平均停靠时间不变的情况下,实施定点停靠措施后．公交车站的服务效率会降低,对停车泊位的需求会增加。     

高架出口匝道区域工程措施实施边界条件研究

针对目前上海市交通高峰期部分出口匝道拥挤严重而面临可能采取工程措施的情况,利用VISSIM仿真软件建模进行出口匝道区域工程措施实施的边界条件研究。以模型中出口匝道车辆排队长度不回溯至主线为条件,确定某个出口匝道的疏散能力(能离开该出口匝道并通过前方交叉口疏散的最大交通量),为今后出口匝道的组织和控制奠定理论基础,并结合现状交通需求,定量确定实施工程措施的充分条件和必要条件,给上海乃至全国高架道路出口匝道区域工程措施实施与否提供理论依据。