Estimating traffic volumes for signalized intersections using connected vehicle data

Recently connected vehicle (CV) technology has received significant attention thanks to active pilot deployments supported by the US Department of Transportation (USDOT). At signalized intersections, CVs may serve as mobile sensors, providing opportunities of reducing dependencies on conventional vehicle detectors for signal operation. However, most of the existing studies mainly focus on scenarios that penetration rates of CVs reach certain level, e.g., 25%, which may not be feasible in the near future. How to utilize data from a small number of CVs to improve traffic signal operation remains an open question. In this work, we develop an approach to estimate traffic volume, a key input to many signal optimization algorithms, using GPS trajectory data from CV or navigation devices under low market penetration rates. To estimate traffic volumes, we model vehicle arrivals at signalized intersections as a time-dependent Poisson process, which can account for signal coordination. The estimation problem is formulated as a maximum likelihood problem given multiple observed trajectories from CVs approaching to the intersection. An expectation maximization (EM) procedure is derived to solve the estimation problem. Two case studies were conducted to validate our estimation algorithm. One uses the CV data from the Safety Pilot Model Deployment (SPMD) project, in which around 2800 CVs were deployed in the City of Ann Arbor, MI. The other uses vehicle trajectory data from users of a commercial navigation service in China. Mean absolute percentage error (MAPE) of the estimation is found to be 9–12%, based on benchmark data manually collected and data from loop detectors. Considering the existing scale of CV deployments, the proposed approach could be of significant help to traffic management agencies for evaluating and operating traffic signals, paving the way of using CVs for detector-free signal operation in the future.     

我国快速公交检票系统布设方法研究

快速公交系统是我国城市公交系统的重要发展方向.合理布设收费系统中的检票系统是保证快速公交系统运营效率的关键环节之一.本文在保证系统整体运营效率的基础上,从检票系统综合成本最小的角度研究检票系统的布设,进而提出了一套快速公交系统检票系统布设的方法.     

Dynamic charging infrastructure deployment for plug-in hybrid electric trucks

Inspired by the rapid development of charging-while-driving (CWD) technology, plans are ongoing in government agencies worldwide for the development of electrified road freight transportation systems through the deployment of dynamic charging lanes. This en route method for the charging of plug-in hybrid electric trucks is expected to supplement the more conventional charging technique, thus enabling significant reduction in fossil fuel consumption and pollutant emission from road freight transportation. In this study, we investigated the optimal deployment of dynamic charging lanes for plug-in hybrid electric trucks. First, we developed a multi-class multi-criteria user equilibrium model of the route choice behaviors of truck and passenger car drivers and the resultant equilibrium flow distributions. Considering that the developed user equilibrium model may have non-unique flow distributions, a robust deployment of dynamic charging lanes that optimizes the system performance under the worst-case flow distributions was targeted. The problem was formulated as a generalized semi-infinite min-max program, and a heuristic algorithm for solving it was proposed. This paper includes numerical examples that were used to demonstrate the application of the developed models and solution algorithms.     

智能交通技术提升快速公交系统性能的研究

智能交通（ITS）技术是快速公交系统（BRT）组成的五大要素之一。本文首先分析BRT和ITS之间的关系。为不同阶层的BRT系统配置合适的ITS技术,并提出一个四阶层BRT系统ITS技术配置框架,最后以北京南中轴路快速公交系统为例来分析其ITS技术配置的合理性。     

Deploying public charging stations for electric vehicles on urban road networks

This paper explores how to optimally locate public charging stations for electric vehicles on a road network, considering drivers’ spontaneous adjustments and interactions of travel and recharging decisions. The proposed approach captures the interdependency of different trips conducted by the same driver by examining the complete tour of the driver. Given the limited driving range and recharging needs of battery electric vehicles, drivers of electric vehicles are assumed to simultaneously determine tour paths and recharging plans to minimize their travel and recharging time while guaranteeing not running out of charge before completing their tours. Moreover, different initial states of charge of batteries and risk-taking attitudes of drivers toward the uncertainty of energy consumption are considered. The resulting multi-class network equilibrium flow pattern is described by a mathematical program, which is solved by an iterative procedure. Based on the proposed equilibrium framework, the charging station location problem is then formulated as a bi-level mathematical program and solved by a genetic-algorithm-based procedure. Numerical examples are presented to demonstrate the models and provide insights on public charging infrastructure deployment and behaviors of electric vehicles.     

Deployment of stationary and dynamic charging infrastructure for electric vehicles along traffic corridors

As charging-while-driving (CWD) technology advances, charging lanes can be deployed in the near future to charge electric vehicles (EVs) while in motion. Since charging lanes will be costly to deploy, this paper investigates the deployment of two types of charging facilities, namely charging lanes and charging stations, along a long traffic corridor to explore the competitiveness of charging lanes. Given the charging infrastructure supply, i.e., the number of charging stations, the number of chargers installed at each station, the length of charging lanes, and the charging prices at charging stations and lanes, we analyze the charging-facility-choice equilibrium of EVs. We then discuss the optimal deployment of charging infrastructure considering either the public or private provision. In the former, a government agency builds and operates both charging lanes and stations to minimize social cost, while in the latter, charging lanes and stations are assumed to be built and operated by two competing private companies to maximize their own profits. Numerical experiments based on currently available empirical data suggest that charging lanes are competitive in both cases for attracting drivers and generating revenue.     

铁路客运专线车站自动售检票终端配置算法

影响车站售票机配置数量的主要因素包括高峰小时旅客发送量、发送旅客超高峰小时系数、站内售票机的售票分担率和售票速度、站房设计的售票厅和进站厅的数量等；影响车站检票机配置数量的主要因素包括高峰小时旅客发送及到达量、到发旅客超高峰小时系数、非常规发送及到达客流波动系数、检票模式、检票机的检票速度、站房设计的出站厅布局以及站台数量等。根据铁路客运专线车站自动售检票系统总体方案，基于对上述影响因素的分析，给出车站自动售检票终端设备配置数量的计算方法。     

Optimal deployment of autonomous vehicle lanes with endogenous market penetration

This paper develops a mathematical approach to optimize a time-dependent deployment plan of autonomous vehicle (AV) lanes on a transportation network with heterogeneous traffic stream consisting of both conventional vehicles (CVs) and AVs, so as to minimize the social cost and promote the adoption of AVs. Specifically, AV lanes are exclusive lanes that can only be utilized by AVs, and the deployment plan specifies when, where, and how many AV lanes to be deployed. We first present a multi-class network equilibrium model to describe the flow distributions of both CVs and AVs, given the presence of AV lanes in the network. Considering that the net benefit (e.g., reduced travel cost) derived from the deployment of AV lanes will further promote the AV adoption, we proceed to apply a diffusion model to forecast the evolution of AV market penetration. With the equilibrium model and diffusion model, a time-dependent deployment model is then formulated, which can be solved by an efficient solution algorithm. Lastly, numerical examples based on the south Florida network are presented to demonstrate the proposed models.     

现代造船模式下应用QFD方法初探

为了更好的适应现代造船模式,在质量控制上必须要有一种能够贯穿船舶设计、建造全过程的系统方法。运用QFD在研制之初,就对建造全过程的质量控制点及要求进行研究,使建造过程的每个关键点都能预先得到有效策划,便于建造过程中加强控制,保证船舶建造的质量。     

铁路客运站自动售票机终端配置微观仿真分析

分析旅客购票过程中的行为特性,基于排队论建立带有止步和中途退出的铁路客运站售票厅排队系统微观仿真模型,以旅客平均排队等待时间最小等为目标函数,就自动售票机的售票分担率和终端配置数量对排队系统的影响进行灵敏度仿真分析.研究结果表明:在自动售票机售票分担率一定时,自动售票机终端的配置数量存在1个阀值,当终端数量超过该阀值时,旅客的平均排队等待时间没有显著减少,在自动售票机终端数量一定时,自动售票机的售票分担率也存在1个阀值,当超过该阀值时会增加旅客平均排队等待时间,使服务水平下降.