A systematic analysis of multimodal transport systems with road space distribution and responsive bus service

A smart design of transport systems involves efficient use and allocation of the limited urban road capacity in the multimodal environment. This paper intends to understand the system-wide effect of dividing the road space to the private and public transport modes and how the public transport service provider responds to the space changes. To this end, the bimodal dynamic user equilibrium is formulated for separated road space. The Macroscopic Fundamental Diagram (MFD) model is employed to depict the dynamics of the automobile traffic for its state-dependent feature, its inclusion of hypercongestion, and its advantage of capturing network topology. The delay of a bus trip depends on the running speed which is in turn affected by bus lane capacity and ridership. Within the proposed bimodal framework, the steady-state equilibrium traffic characteristics and the optimal bus fare and service frequency are analytically derived. The counter-intuitive properties of traffic condition, modal split, and behavior of bus operator in the hypercongestion are identified. To understand the interaction between the transport authority (for system benefit maximization) and the bus operator (for its own benefit maximization), we examine how the bus operator responds to space changes and how the system benefit is influenced with the road space allocation. With responsive bus service, the condition, under which expanding bus lane capacity is beneficial to the system as a whole, has been analytically established. Then the model is applied to the dynamic framework where the space allocation changes with varying demand and demand-responsive bus service. We compare the optimal bus services under different economic objectives, evaluate the system performance of the bimodal network, and explore the dynamic space allocation strategy for the sake of social welfare maximization.     

浅谈交通组织在城市道路设计中的应用

本文通过对道路红线、绿线的搭配使用 ,兼顾交通功能和景观功能的前提下 ,在道路平面设计阶段纳入交通组织设计 ,并通过绿化和车道板块分割实现功能划分 ,以体现交通组织在道路设计中的重要意义 ,旨在对交通组织在道路中的实际应用进行探讨和实践。     

Modeling the impacts of mandatory and discretionary lane-changing maneuvers

In this paper, a novel mesoscopic multilane model is proposed to enable simultaneous simulation of mandatory and discretionary lane-changing behaviors to realistically capture multilane traffic dynamics. The model considers lane specific fundamental diagrams to simulate dynamic heterogeneous lane flow distributions on expressways. Moreover, different priority levels are identified according to different lane-changing motivations and the corresponding levels of urgency. Then, an algorithm is proposed to estimate the dynamic mandatory and discretionary lane-changing demands. Finally, the lane flow propagation is defined by the reaction law of the demand–supply functions, which can be regarded as an extension of the Incremental-Transfer and/or Priority Incremental-Transfer principles. The proposed mesoscopic multilane cell transmission model is calibrated and validated on a complex weaving section of the State Route 241 freeway in Orange County, California, showing both the positive and negative impact of lane changing maneuvers, e.g., balancing effect and capacity drop, respectively. Moreover, the empirical study verifies that the model requires no additional data other than the cell transmission model does. Thus, the proposed model can be deployed as a simple simulation tool for accessing dynamic mesoscopic multilane traffic state from data available to most management centers, and also the potential application in predicting the impact of traffic incident or lane control strategy.     

Understanding the impacts of a combination of service improvement strategies on bus running time and passenger’s perception

Transit agencies implement many strategies in order to provide an attractive transportation service. This article aims to evaluate the impacts of implementing a combination of strategies, designed to improve the bus transit service, on running time and passenger satisfaction. These strategies include using smart card fare collection, introducing limited-stop bus service, implementing reserved bus lanes, using articulated buses, and implementing transit signal priority (TSP). This study uses stop-level data collected from the Société de transport de Montréal (STM)’s automatic vehicle location (AVL) and automatic passenger count (APC) systems, in Montréal, Canada. The combination of these strategies has lead to a 10.5% decline in running time along the limited stop service compared to the regular service. The regular route running time has increased by 1% on average compared to the initial time period. The study also shows that riders are generally satisfied with the service improvements. They tend to overestimate the savings associated with the implementation of this combination of strategies by 3.5-6.0 min and by 2.5-4.1 min for both the regular route and the limited stop service, respectively. This study helps transit planners and policy makers to better understand the effects of implementing a combination of strategies to improve running time and passenger’s perception of these changes in service.     

平面交叉口港湾式左转车道安全设计

在平面交叉口交通事故中,与左转相关的事故占较大比例,而设置港湾式左转车道,可有效改善平交路口的交通安全状况。分析左转车辆对交叉口安全性的影响,确定设置港湾式左转车道的主要因素,并结合国内外研究,从左转车道的长度和宽度等方面对左转车道的设计进行探讨,提出平面交叉口港湾式左转车道的安全设计方法并分析其安全效益。     

山区公路交通安全保障措施模拟评价

以云南小磨路K109+600~K122+024路段上的隧道群、陡坡与混行路段为试验样本路段, 应用虚拟视景生成系统建立了路段三维静态与动态模型。在隧道内设置倒伏示警柱、视觉标线与常规标线3种中央隔离设施, 在爬坡路段与混行路段上均设置附加车道, 对比分析了3种路段上的平均车速与车辆平均横向位置, 并评价了3种安全保障措施的效果。分析结果表明: 在隧道内, 3种中央隔离设施下的平均车速标准差分别为9.74、10.01、10.40 km·h^-1, 车辆平均横向位置标准差分别为0.54、0.70、0.69 m, 说明设置倒伏示警柱后, 车辆保持较好车速和横向位置; 在爬坡路段上, 当交通流量不超过1 000 pcu·h^-1时, 设置附加车道有利于主线路车辆车速的提高; 在混行路段上, 当非机动车流量分别为500、800 pcu·h^-1时, 设置附加车道后, 车速增大, 车速标准差减小, 车辆横向位置变大, 说明设置附加车道有利于提高和稳定车速, 并可减少与对向车辆的冲突。     

大城市中心区近期公交专用道体系构建初探——以杭州市为例

随着城市化和机动化的快速发展,城市交通拥堵日益加剧,"公交优先"已引起广泛的重视,而公交专用道是最重要的公交优先路权保障措施。该文对公交专用道的发展背景和发展趋势进行了分析,并以杭州市公交专用道体系设置为例,在大城市公交专用道的体系构建流程研究的基础上提出公交专用道的相关配套设施实施建议,旨在说明公交专用道体系建设时,须同步建设公交换乘枢纽、调整优化公交线路等配套设施,方可发挥公交专用道体系的规模效应,引导市民出行方式转变。     

考虑弯道几何要素和交通量影响的汽车行驶速度预测模型

为了实现对弯道半径、转角、路宽等多个几何线形要素的协同控制,选取了14个有代表性的运行速度模型,使用回归方法建立了侧向容许加速度模型,用其可以计算出半径为R的弯道速度;提出了等效半径的概念,即车辆在曲中位置的实际轨迹半径Re,通过对Re观测数据的回归分析,分别获得了曲线转角影响模型和通道宽度影响模型;最后分析了不同半径条件下交通量对行驶速度的影响,通过求出平均行驶速度与运行速度之间的差值ΔV,建立了ΔV与R和交通量之间的关系模型,并对3条公路运行速度进行了仿真。结果表明：应用该模型得到的运行速度曲线能够同时反映出弯道半径、转角、通道宽度的影响,能够帮助设计者实现对这3个要素的协同控制;根据速度曲线还可以获得不同交通量水平下的旅行时间,进而预测出所设计公路的服务水平。     

现代有轨电车交叉口交通组织研究

现代有轨电车通常采用地面线路,其在城市道路断面中的布置形式以及在交叉路口的交通组织形式对有轨电车的运营效率和城市交通运输系统有重要影响.对现代有轨电车路权分类、车道布置形式、交叉路口交通组织方式进行了分析,为我国城市发展现代有轨电车提供参考.     

公交专用道的运行状态及对社会车道的影响

本文提出了一种分析已有公交专用道运行状态的方法.通过计算公交车道和社会车道上的饱和度,来确定公交车道和社会车道的服务水平,并结合公交专用道上各车型所占比例,分析公交专用道的运行情况及其对社会车道的影响,指出存在的问题和可能的改进措施.