A probabilistic optimization model for allocating freeway sensors

This paper proposes a sensor location model to identify a sensor configuration that minimizes overall freeway performance monitoring errors while considering the consequences of probabilistic sensor failures. To date, existing sensor location models for freeway monitoring inherently assume that either deployed sensors never fail or the consequences of sensor failure are trivial matters. However, history has revealed that neither assumption is realistic, suggesting that ignoring failures in sensor allocation models may actually produce a significantly suboptimal configuration in the real world. Our work addresses this dilemma by developing a probabilistic optimization model that will minimize the error expectation by examining all possible failure scenarios, each with an occurrence probability. To ensure the scenario completeness and uniqueness, a sensor failure scenario is represented by using a binary string with 1 indicating an operational sensor at a given site and 0 for sensor failure or no sensor deployed. When applied to a case study network, it is shown that an optimal configuration that considers sensor failure is significantly different from an optimal configuration that ignores sensor failure, revealing that sensor failures pose non-trivial consequences on performance monitoring accuracy.     

The design of electric vehicle charging network

The promotion of Electric Vehicles (EVs) has become a key measure of the governments in their attempt to reduce greenhouse gas emissions. However, range anxiety is a big barrier for drivers to choose EVs over traditional vehicles. Installing more charging stations in appropriate locations can relieve EV drivers’ range anxiety. To determine the locations of public charging stations, we propose two optimization models for two different charging modes - fast and slow charging, which aim at minimizing the total cost while satisfying certain coverage goal. Instead of using discrete points, we use geometric objects to represent charging demands. Importantly, to resolve the partial coverage problem (PCP) for networks, we extend the polygon overlay method to split the demands on the road network. After applying the models to Greater Toronto and Hamilton Area (GTHA) and to Downtown Toronto, we show that the proposed models are practical and effective in determining the locations of charging stations. Moreover, they can eliminate PCP and provide much more accurate results than the complementary partial coverage method (CP).     

A toll-based bi-level programming approach to managing hazardous materials shipments over an intermodal transportation network

This research proposes a bi-level bi-objective model to regulate the usage of rail intermodal terminals for hazardous materials (hazmat) shipments, where government imposes tolls to deter carriers from using certain terminals. The complexity of the resulting mathematical program motivates the development of a hybrid speed-constrained multi-objective particle swarm optimization algorithm, which is then integrated with CPLEX, to solve the model. Through a real problem instance based on the intermodal service chain of Norfolk Southern in US, the toll-setting model is examined and further compared with a regular network design approach, in which certain terminals are closed to hazmat containers. The computational results show that the toll-setting policy is more practical and efficient, and the two models can be combined as a two-stage strategy in long-term hazmat transportation regulations. Additional managerial insights are derived for different stakeholders.     

Applying spatial-temporal analysis and retail location theory to public bikes site selection in Taipei

In order to turn Taipei into a sustainable, green metropolis, in 2009, the Department of Transportation of Taipei City Government launched a public bike rental system (YouBike) to meet people’s daily commute and/or leisure needs. Given that users may return bikes to sites differing from their starting locations, rental stations frequently lack bikes or bike racks. This study sought to identify lacking-bike and/or lacking-bike rack hot spots utilizing spatial-temporal analysis. In addition, it applied retail location theory to determine site selection of further rental stations. Historical data indicated that shortage of bikes was much more severe than shortage of bike racks in the YouBike public bike system and lacking-bike and lacking-bike rack hot spots were clustered significantly. The study demonstrated that spatial-temporal analysis can be used to effectively identify rental stations’ spatial patterns, determine the most suitable locations for further installation of rental stations, help to provide public bike users with a more effective rental system, and greatly assist public bikes’ operational management and decision-making in Taiwan.     

地铁车站出入口设施优化设置研究

闸机检票效率影响地铁车站的整体通行能力,且作用于乘客等待时间来影响社会效益。为此,从系统优化的角度出发,以稳态条件下单位时间总费用为目标函数,通过研究北京西直门地铁枢纽A口客流出入站的过程,分析影响闸机设置的因素,以客流需求、空间限制、成本投入、疏散要求等为约束条件,采用线性规划的方法,对闸机设置进行优化研究,分别确定普通闸机与加宽闸机的个数。根据优化结果,为科学组织高峰小时客流出入车站提供基础数据和重要参考,检验实设闸机的合理程度。     

城市轨道交通与地面常规公共交通的客运一体化

探讨基于城市轨道交通的地面常规公共交通线路布局、城市轨道交通与地面常规公共交通客运一体化的换乘布局、无缝换乘和票制协调。提出在大力发展城市轨道交通的同时．应注重实施“城市轨道交通与地面常规公共交通的客运一体化”——以城市轨道交通为主,以常规公共交通为辅,实现城市轨道交通与地面常规公共交通紧密衔接。     

基于多源数据的北京轨道交通客流特征分析

为提高城市轨道交通成网条件下客流预测与运营管理水平,有必要对轨道交通客流特征进行研究。结合实地调研数据,利用海量的市政交通"一卡通"(IC卡)数据和移动通信定位数据对北京市轨道交通乘客属性特征、时空特征、接驳特征、票价调整影响特征等进行分析,最后对客流需求高增长的北京轨道交通客流特征进行总结。结果表明:北京轨道交通工作日主要服务于中低收入的中青年通勤族,77.25%的乘客轨道交通出行时间在10~60 min之间;轨道交通线路高峰客流有明显的潮汐现象,受职住分离现象的影响,客流空间分布的不均衡性突出;现阶段轨道交通网络发展较为成熟,但仍有部分区域对轨道交通的需求较大;轨道交通站点接驳设施的便利性和完善性程度影响乘客对轨道站点交通方式的选择;在可接受范围内,票价调整对客流的影响在短期内较明显,经过渡期后客流量呈增加趋势。     

徐州轨道交通1号线彭城广场站方案比选

以徐州轨道交通1号线彭城广场站为例,以位于商业中心同期实施换乘车站方案的合理性和综合开发能力为研究目的,通过对彭城广场站规划线路外部控制条件的分析,深入讨论在车站站位、站型、换乘形式、联络线的设置等存在多种可能性的情况下,如何设计出满足车站功能、换乘功能、车站及区间可实施性、客流吸引、综合开发、综合造价、运营安全以及社会效益等要求的建筑方案,并筛选出具有代表性、可比性的方案进行综合比选,以确定推荐方案。同时针对位于城市中心且控制性因素较多的车站建筑设计提出一些有价值的意见和建议。     

航空联运时代物流中枢机场选择研究

经济全球化、电子商务、第三方物流等多种因素促使中国航空联运业务快速增长,正在重塑中国航空货运网络。首先从中国参与全球经贸一体化程度加深、城市群产业转型升级与布局优化、航空物流快速发展等方面对中国现阶段发展航空联运的必要性及趋势进行分析。然后建立模型对国际与国内物流中枢机场选择进行分析,显示郑州新郑、武汉天河两机场具备中枢机场建设条件。进而对两机场的现状基础及潜力进行深度考察,认为二者在建设国际与国内物流中枢机场方面各具优势,应当考虑错位发展。     

基于熵权-ANP模型的自行车租赁点选址问题

为了寻求自行车租赁点的最优选址,从其多目标决策的特点出发,以网络层次分析法(ANP)为基本框架,把换乘时间、吸引距离及土地成本等作为决策指标,同时,创新性地引入熵权,计算和分析各个决策指标间相互影响的程度,最终建立熵权-ANP 模型。通过一个实例,验证了该模型能客观地对决策方案做出定量分析,得到决策结论。