Using SenseCam to pursue “ground truth” for global positioning system travel surveys

Global Positioning System (GPS) surveys have been conducted for the past decade. Although GPS records were initially regarded as providing “ground truth” of travel, it has been found subsequently that they have some errors. SenseCam, a small passive digital camera, provides a chance to pursue ground truth by capturing images every 20 s on average. This paper discusses how SenseCam could help GPS data collection and shows potential benefits for both SenseCam and GPS research. This paper also investigates the performance of GPS devices in detail in terms of recording data by comparisons between GPS results and SenseCam images. The specific issue of missing GPS data is discussed and examined in this paper.     

User perspectives in public transport timetable optimisation

The present paper deals with timetable optimisation from the perspective of minimising the waiting time experienced by passengers when transferring either to or from a bus. Due to its inherent complexity, this bi-level minimisation problem is extremely difficult to solve mathematically, since timetable optimisation is a non-linear non-convex mixed integer problem, with passenger flows defined by the route choice model, whereas the route choice model is a non-linear non-continuous mapping of the timetable. Therefore, a heuristic solution approach is developed in this paper, based on the idea of varying and optimising the offset of the bus lines. Varying the offset for a bus line impacts the waiting time passengers experience at any transfer stop on the bus line.In the bi-level timetable optimisation problem, the lower level is a transit assignment calculation yielding passengers’ route choice. This is used as weight when minimising waiting time by applying a Tabu Search algorithm to adapt the offset values for bus lines. The updated timetable then serves as input in the following transit assignment calculation. The process continues until convergence.The heuristic solution approach was applied on the large-scale public transport network in Denmark. The timetable optimisation approach yielded a yearly reduction in weighted waiting time equivalent to approximately 45 million Danish kroner (9 million USD).     

About the possibilities of using the renewable energy power sources on railway transport

Several electrification systems based on renewable energy power sources (first of all, solar energy) are discussed in respect to their applicability to railway transport and, in particular, to suburban electric trains. Two systems are considered with basic technical details and economic estimation, both including the onboard bank of batteries and the photovoltaic converters (PVC) of solar energy for compensation of energy expenses, which could be positioned either on stations or on wagon's roofs. Sun‐tracking systems and their effect on the solar energy conversion efficiency are discussed in application to stationary and moving PVC platforms. An analysis made shows that introduction of the “green” systems discussed will not only have positive ecological impact, but also can bring a notable economical effect even with today's components, while it could be considerably greater with the usage of new PVCs, which are being developed by the authors. Copyright © 2011 John Wiley & Sons, Ltd.     

Boundedly rational user equilibria (BRUE): Mathematical formulation and solution sets

Boundedly rational user equilibria (BRUE) represent traffic flow distribution patterns where travellers can take any route whose travel cost is within an ‘indifference band’ of the shortest path cost. Those traffic flow patterns satisfying the above condition constitute a set, named the BRUE solution set. It is important to obtain all the BRUE flow patterns, because it can help predict the variation of the link flow pattern in a traffic network under the boundedly rational behavior assumption. However, the methodology of constructing the BRUE set has been lacking in the established literature. This paper fills the gap by constructing the BRUE solution set on traffic networks with fixed demands. After defining ε-BRUE, where ε is the indifference band for the perceived travel cost, we formulate the ε-BRUE problem as a nonlinear complementarity problem (NCP), so that a BRUE solution can be obtained by solving a BRUE–NCP formulation. To obtain the BRUE solution set encompassing all BRUE flow patterns, we propose a methodology of generating acceptable path set which may be utilized under the boundedly rational behavior assumption. We show that with the increase of the indifference band, the acceptable path set that contains boundedly rational equilibrium flows will be augmented, and the critical values of indifference band to augment these path sets can be identified by solving a family of mathematical programs with equilibrium constraints (MPEC) sequentially. The BRUE solution set can then be obtained by assigning all traffic demands to the acceptable path set. Various numerical examples are given to illustrate our findings.     

城际铁路列车开行方案优化分析

列车开行方案对城际铁路的运营组织至关重要,并直接影响着城际铁路运营效益。文中从旅客平均候车时间出发,提出城际旅客出行方便值的概念,基于城际铁路旅客出行方便值最大和运营组织效益最优,建立城际铁路客车开行方案优化模型,并设计该模型相应的算法。对城际铁路的运营管理决策有很好的借鉴意义。     

高普速场互联互通时场联及列控系统方案研究

客运专线高速场与既有线普速场并站互联互通的情况在实际工程应用中越来越多,此时两场间联络线信号机设置情况及普速场列控、联锁设置方案比较复杂.以张呼铁路呼和浩特东站(含高、普速场)为例,详细分析普速场联锁及列控设置的最佳方案,并根据联络线长短分别给出高、普速场间联络线信号机设置最优方案:联络线较短时,因无法设置信号机,可由...     

列车晚点情况下的地铁运营调整自组织机制研究

在细致梳理他组织模式下的列车运行调整规则与策略基础上,引入智能体概念,借鉴“沙丁鱼群”运动效应,将邻近两列车间的运行时间距离划分为排斥间隔、协同间隔和吸引间隔,继而建立列车间的协同运动关系.运用仿真技术实现了晚点情况下的列车运行调整自组织算例,论证了自组织调整机制的有效性和应用性.     

基于粒子群算法的城轨列车节能驾驶优化模型

为了降低城市轨道交通中列车在站间运行的能耗, 研究了列车的站间节能驾驶策略, 在考虑线路限速和坡度的情况下, 建立了时间约束下的列车节能优化模型, 采用粒子群算法优化目标速度序列得出了列车节能驾驶策略。节能驾驶优化方法通过2个阶段来实现, 第1阶段在站间运行时间不变的情况下, 采用粒子群算法优化了列车在站间的节能驾驶策略, 得到了运行时间和能耗的关系, 第2阶段在多站间总运行时间不变的前提下, 将运行时间进行重新分配, 得到了列车在全线运行的节能驾驶策略。以北京地铁亦庄线实际线路数据和车辆参数为基础, 对优化方法进行仿真验证。仿真结果表明: 经过第1阶段的优化, 列车在万源街-荣京东街的单站间运行能耗降低了6.15%, 经过第2阶段的优化, 列车在多站间总运行能耗降低了14.77%。可见, 优化模型可以有效降低列车的运行能耗, 为列车时刻表的编制提供依据。     

铁路枢纽内快运班列车流组织的鲁棒优化研究

针对当前生产运营中较少考虑货运站点货物需求不确定性以及客户对货物运到期限的要求,设计双层时空服务网络描述枢纽内快运班列车流组织过程.该网络分为货源层和编组层,货源层中带有方向别的车流选择延迟弧或运输弧在相应时段到达编组层中的编组站.同时考虑编组站办理方向总数和车流组织基本约束,构建了铁路枢纽内快运班列车流组织鲁棒优化模型(CR),使用IBMILOG Cplex软件对模型进行精确求解.通过算例和大规模测试进行验证分析,结果表明,当ω=0.03时,鲁棒模型的目标函数值比随机优化模型(CS)的目标函数值降低5.10%,发送车数提高5.66%,最长求解时间为82 s,鲁棒性强于随机优化模型.虽然确定性模型(CD)在—些情景下可以获得较优的解,但是在需求不确定的条件下,确定性模型目标函数值要差于随机优化模型和鲁棒模型.当枢纽内货运站点数设为50时,时空网络服务弧段数达317,模型的求解时间为1 375.4 s,在可以接受的时间范围内.     

基于正态云模型和模糊层次分析法的列车通信网络性能评估方法

为保证高速列车安全、可靠运行,研究了列车通信网络性能评估方法;综合考虑列车通信网络的实时性、可靠性和服务质量,建立了合理的列车通信网络性能评价指标体系,采用模糊层次分析法确定列车通信网络性能评估指标的权重;考虑列车通信网络评估过程中具有不确定性,构建了基于正态云模型和模糊熵的二维评估模型;建立了基于交换式以太网的大容量和高可靠性列车通信网络仿真平台,获取各指标样本数据,运用二维评估模型计算各指标的隶属度,依据模糊理论最大隶属度法则确定列车通信网络性能等级。研究结果表明：在列车通信网络状态良好时,60%评估样本的网络性能等级为Ⅰ、Ⅱ级,在网络丢包率和误码率较大时,40%评估样本的评估等级为Ⅲ、Ⅳ级,表明二维评估模型能够有效地反映列车通信网络状态;与仅运用模糊综合评价法相比较,两者的评估结果基本一致,反映了二维评估模型的准确性;模糊综合评价法不能消除评估过程中不确定性因素的影响,从而导致评估结果缺乏精确度,因此,提出的方法更适合于列车通信网络性能评估。