信号控制交叉口左转非机动车过街模式适用性

为分析信号控制交叉口两种左转非机动车过街模式（机动车和非机动车一体化模式以及行人和非机动车一体化模式）的适用条件,在动态交通条件下,定量分析两种模式对典型两相位和四相位信号控制交叉口通行效率和安全性的单独与综合影响。在通行效率方面,选取机动车通行能力作为评价指标;在安全性方面,引入一个可比选交通设计方案的指标——交通当量冲突。通过理论与实例分析,从通行效率和安全性两方面给出了两种模式的适用性。结果表明：两种模式在上述方面均有单独优势;两相位信号控制交叉口,在相应的左转非机动车和机动车交通量条件下两种模式均能同时提高交叉口通行效率和安全性;四相位信号控制交叉口,两种模式均不能同时起到积极作用。     

The effect of crowding on public transit user travel behavior in a large-scale public transportation system through modeling daily variations

In this paper, the crowding effect in a transit vehicle is modeled in a time-expanded network that considers the daily variation in passenger flows. The study models the daily variation of in-vehicle crowding in a real large-scale transit system. A transit assignment for this real network is modeled and implemented by constructing a crowding cost function that follows the valuation of crowding and by using the reliable shortest path finding method. The direct application of the crowding model to a real network for the Utah Transit Authority indicates that crowd modeling with multi-user classes could influence public transportation system planning and affect the revenues of transit agencies. Moreover, the addition of the disutility factor, crowding, does not always appear to cause an increase in disutility for transit users.     

Innovative strategies for urban car-sharing systems and a simulator to assess their performance

In this paper, three innovative car-sharing systems for urban areas are proposed, based on fleets of individual intelligent vehicles with three service characteristics: instant access, open-ended reservations and one-way trips. These features provide high flexibility but create an uneven distribution of vehicles among stations. Therefore, relocation of vehicles must be performed. Three different system procedures are proposed: in the first system, relocations are performed by users; in the other two, vehicles relocate automatically, thanks to their automation. In the first two systems, vehicles are accessible only at stations, whereas in the third they are also accessible along roads. In order to provide transport managers with a tool to test systems in different realities, an object-oriented simulator is developed. The simulation provides outputs of system performance, in terms of user waiting times and system efficiency. The proposed systems are simulated for the city of Genoa, in Italy, and a comparative analysis is presented.     

Instantaneous communication throughputs of vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) formed by connected vehicles in a traffic stream could be applied to improve safety, mobility, and environmental impacts of a transportation system. In this paper, we present analytical models for the instantaneous communication throughputs of VANETs to measure the efficiency of information propagation under various traffic conditions at a time instant. In particular, we define broadcast and unicast communication throughputs by the wireless channel bandwith multiplied by the average probabilities that one vehicle is a successful receiver and sender in a VAENT, respectively. With a protocol communication model, we derive formulas to determine the probabilities for an equipped vehicle to be a successful broadcast receiver and a successful unicast receiver/sender, and obtain broadcast and unicast throughputs along discrete and continuous traffic streams. We further examine the impacts on communication throughputs of the transmission range and the interference range of dedicated short range communication devices as well as the market penetration rate of equipped vehicles and the percentage of senders. Finally, we investigate the influence of shock waves on communication throughputs.     

汽车排放污染及净化对策研究

阐述汽车排放污染物的成分及其危害,介绍新排放法规Ⅰ型、Ⅲ型、Ⅳ型试验限值,重点分析汽车的5项排放影响因素及其净化措施。     

地铁列车逻辑控制电路安全服役技术应用研究

为克服传统地铁列车继电器控制电路高故障率和无记录功能等诸多缺陷,提出了基于新型二乘二取二技术的无触点逻辑控制方案.完成了系统架构设计包括热备冗余、网络通信、故障诊断、日志分析等功能.针对既有地铁列车进行了控制电路技术方案设计和施工改造,首先在分析原有控制回路原理的基础上,完成无触点逻辑控制单元替代继电器点位设计;然后综...     

军运保障中高原和山区对汽车性能的影响及对策

从高原和山区的海拔高度及地理环境等对汽车的动力和制动性的影响入手,分析了高原和山区汽车运输的特点,并根据部队的使用经验和试验结论,提出了改善发动机性能和改进汽车制动系的措施,为高原和山区的车辆装备综合管理及技术保障提供了科学的依据。     

智能网联车环境下高速匝道汇入车流轨迹优化模型

为了解决传统匝道控制车流汇入时车辆需要减速至停止,从而造成延误时间过长的问题,提出了一种智能网联车环境下的高速匝道汇入车辆轨迹优化的两阶段优化模型,其中,第1 阶段优化车辆进入匝道口的时序;第2 阶段基于第1 阶段的最优时序,优化车辆轨迹. 根据所构建的模型设计了一种启发式算法优化车辆通过匝道冲突区域的时序,然后结合 GPOPS工具优化车辆的轨迹.为了验证所提出方法的有效性,将所提出的方法应用到20 min 随机到达的车流,进行仿真实验.实验结果表明,与先进先出的方法相比,本文所提出的方法能够使总延误减少59.7%,总油耗减少10.5%,说明该方法能够实现车辆以较高的速度通过匝道冲突区域,有效地减少了车辆汇入延误,同时也节约了油耗.     

Smarter and more connected: Future intelligent transportation system

Emerging technologies toward a connected vehicle-infrastructure-pedestrian environment and big data have made it easier and cheaper to collect, store, analyze, use, and disseminate multi-source data. The connected environment also introduces new approaches to flexible control and management of transportation systems in real time to improve overall system performance. Given the benefits of a connected environment, it is crucial that we understand how the current intelligent transportation system could be adapted to the connected environment.     

Flow-field guided steering control for rigid autonomous ground vehicles in low-speed manoeuvring

ABSTRACT

This paper studies the low-speed manoeuvring problem for autono-mous ground vehicles operating in complex static environments. Making use of the intrinsic property of a fluid to naturally find its way to an outflow destination, a novel guidance method is proposed. In this approach, a reference flow field is calculated numerically through Computational Fluid Dynamics, based on which both the reference path topology and the steering reference to achieve the path are derived in a single process. Steering control considers three constraints: obstacle and boundary avoidance, rigidity of the vehicle, plus the non-holonomic velocity constraints due to the steering system. The influences of the parameters used during the flow field simulation and the control algorithm are discussed through numerical cases. A divergency field is defined to evaluate the quality of the flow field in guiding the vehicle. This is used to identify any problematic branching features of the flow, and control is adapted in the neighbourhood of such branching features to resolve possible ambiguities in the control reference. Results demonstrate the effectiveness of the method in finding smooth and feasible motion paths, even in complex environments.