移动荷载作用下沥青路面动态响应三维有限元分析

我国新建道路沥青路面是以双轮组单轴载100 kN(BZZ-100)为标准轴载,采用双圆均布荷载作用下的多层弹性理论进行设计的,而汽车实际施加给路面的是移动荷载。通过建立半刚性基层路面的三维有限元分析模型,对汽车匀速行驶及制动情况下路面的动态响应进行了有限元分析,得出了荷载正下方不同深度处节点竖向位移、竖向压应力、水平应力、竖向剪应力及水平剪应力的时间历程曲线,并与静载作用下的计算结果进行了对比分析。     

������·�ڽ�ͨ�ź���ƣ�����ģ�ͼ����·����ıȽ����ܽ�

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.     

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.     

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.     

Operation of signalized diamond interchanges with frontage roads using dynamic reversible lane control

Signalized diamond interchanges (SDI), connecting major highways and surface streets in urban and suburban areas, are probably the most widely used interchange patterns. The limited storage space between the two closely joined intersections coupled with heavy traffic volumes may easily oversaturate the facility and cause spillback problems, especially with the presence of frontage roads. This paper presents an innovative design and operational model for SDI by dynamically reversing certain lanes in the internal link on a regular basis with the deployment of overhead reversible lane control signs. A Binary-Mixed-Integer-Linear-Program (BMILP) is formulated to simultaneously optimize lane markings, dynamic usage of the reversible lane, and signal timings for the new SDI system. Results from extensive numerical analyses reveal the promising property of the proposed design and operational model in expanding capacity and reducing congestion at the SDI with frontage roads.     

A trajectory smoothing method at signalized intersection based on individualized variable speed limits with location optimization

Traffic signals on urban highways force vehicles to stop frequently and thus causes excessive travel delay, extra fuel consumption and emissions, and increased safety hazards. To address these issues, this paper proposes a trajectory smoothing method based on Individual Variable Speed Limits with Location Optimization (IVSL-LC) in coordination with pre-fixed traffic signals. This method dynamically imposes speed limits on some identified Target Controlled Vehicles (TCVs) with Vehicle to Infrastructures (V2I) communication ability at two IVSL points along an approaching lane. According to real-time traffic demand and signal timing information, the trajectories of each approaching vehicle are made to run smoothly without any full stop. Essentially, only TCVs’ trajectories need to be controlled and the other vehicles just follow TCVs with Gipps’ car-following model. The Dividing RECTangles (DIRECT) algorithm is used to optimize the locations of the IVSLs. Numerical simulation is conducted to compare the benchmark case without vehicle control, the individual advisory speed limits (IASL) and the proposed IVSL-LC. The result shows that compared with the benchmark, the IVSL-LC method can greatly increase traffic efficiency and reduce fuel consumption. Compared with IASL, IVSL-LC has better performance across all traffic demand levels, and the improvements are the most under high traffic demand. Finally, the results of compliance analysis show that the effect of IVSL-LC improves as the compliance rate increases.     

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.     

Real-time estimation of turning movement counts at signalized intersections using signal phase information

A variety of sensor technologies, such as loop detectors, traffic cameras, and radar have been developed for real-time traffic monitoring at intersections most of which are limited to providing link traffic information with few being capable of detecting turning movements. Accurate real-time information on turning movement counts at signalized intersections is a critical requirement for applications such as adaptive traffic signal control. Several attempts have been made in the past to develop algorithms for inferring turning movements at intersections from entry and exit counts; however, the estimation quality of these algorithms varies considerably. This paper introduces a method to improve accuracy and robustness of turning movement estimation at signalized intersections. The new algorithm makes use of signal phase status to minimize the underlying estimation ambiguity. A case study was conducted based on turning movement data obtained from a four-leg signalized intersection to evaluate the performance of the proposed method and compare it with two other existing well-known estimation methods. The results show that the algorithm is accurate, robust and fairly straightforward for real world implementation.     

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...