The punctuality performance of aircraft rotations in a network of airports

The aim of this paper is to investigate the influence of aircraft turnaround performance at airports on the schedule punctuality of aircraft rotations in a network of airports. A mathematical model is applied, composed of two sub-models, namely the aircraft turnaround model (turnaround simulations) and the enroute model (enroute flight time simulations). A Markovian type model is featured in the aircraft turnaround model to simulate the operation of aircraft turnarounds at an airport by considering operational uncertainties and schedule punctuality variance. In addition, stochastic Monte Carlo simulations are employed to carry out stochastic sampling and simulations in both the aircraft turnaround model and the enroute model. Results of simulations show the robustness of the aircraft rotation model in capturing uncertainties from aircraft rotations. The propagation of knock-on delays in aircraft rotations is found to be significant when the short-connection-time policy is used by an airline at its hub airport. It is also found that the proper inclusion of schedule buffer time in the aircraft rotation schedule helps control the propagation of knock-on delays and, therefore, stabilize the punctuality performance of aircraft rotations.     

Book reviews

THE SEVENTH AUSTRALIAN TRANSPORT RESEARCH FORUM, by K. W. Ogden.

AIRLINE PLANNING: CORPORATE, FINANCIAL AND MARKETING by Nawal K. Taneja. Lexington, Mass., Lexington Books, 1982. 207 pp. (£19.50)

SOLVING LOCAL GOVERNMENT PROBLEMS: PRACTICAL APPLICATIONS OF OPERATIONS RESEARCH IN CITIES AND REGIONS, by Charles E. Pinkus and Anne Dixson. George Allen and Unwin, London, 1981. (Hardback £20.00; paperback £8.95)

SCIENTIFIC MANAGEMENT OF TRANSPORT SYSTEMS, edited by N. K. Jaismal. Published by North‐Holland Publishing Company (U.S. $58.50)

TRANSPORTATION AND TRAFFIC ENGINEERING HANDBOOK (Second Edition), edited by W. S. Homburger, Englewood Cliffs, N.J., 1982. Prentice Hall, pp. 883.

ECONOMICS OF PUBLIC TRANSPORT, by C. A. Nash. Longman, London, pp. 194. (£6.95).     

LMS自适应时延估计法在被动定位系统中的应用研究

小均方（ＬＭＳ）自适应时延估计法不依赖于输入信号和噪声的统计先验知识而可以跟踪动态或时变的环境和参数,算法亦比较简单。计算机仿真和湖试分析数据分析表明,将ＬＭＳ自适应时延估计法应征地被动定位系统,可以获得较高的定位精度,另外,对影响被动定位精度的因素进行了分析。     

Overtaking assistant assessment using traffic simulation

This contribution presents the results of a microscopic traffic simulation study of the potential effects of an overtaking assistant for two-lane rural roads. The overtaking assistant is developed to support drivers in judging whether or not an overtaking opportunity can be accepted based on the distance to the next oncoming vehicle. Drivers have been found to consider this to be a difficult part of an overtaking manoeuvre. The assistant’s effects on traffic efficiency, driver comfort and road safety have been investigated using traffic simulation. The results indicate that this type of overtaking assistant can provide safety benefits in terms of increased average time-to-collision to the next oncoming vehicle during overtaking manoeuvres. This safety benefit can be achieved without negative consequences for traffic efficiency and driver comfort. A driver assistance system that supports the distance judging part of overtaking manoeuvres can therefore contribute to improved traffic conditions on the two-lane rural roads of the future.     

基于多智能体的城市轨道交通列车延误仿真模型与应用

城市轨道交通列车延误处置方案制定是轨道交通运营管理的重要工作,处置方案的合理性是提高处置效率的前提,验证处置方案的合理性也是运营管理部门急待解决的问题。基于此,以多智能体（以下简称多Agent）理论为基础,分别构建乘客Agent、列车Agent、网络Agent及突发事件Agent的仿真模型;分析列车延误的多Agent仿真原理;以上海轨道交通2号线列车延误为背景,编写多Agent列车延误仿真程序,并对处置方案进行仿真分析,该模型已在上海轨道交通人民广场站大客流处置工作中得到了实际应用。     

冻融循环条件下延迟时间对水泥改良低液限粉土动力特性影响试验研究

模拟路基真实的冻融循环过程,设计冻融试验,制作冻融试验箱,进行改良土试样的冻融循环试验。通过动三轴试验,研究在冻融条件下,延迟时间对水泥改良低液限粉土的动强度、动弹性模量、动变形以及超孔隙水压力的影响。结果表明:在相同的冻融次数下,动强度和破坏循环次数随着延迟时间的增加而降低;在相同的冻融次数及一定动荷载幅值作用下,屈服应变则随着延迟时间的增加而增加;延迟时间短的试样,动弹性模量值较大,但随应变的衰减较平缓,且趋于一个稳定值;不同延迟时间试样达到相同应变幅值时所增长的孔压值不同,延迟时间越长,孔压越大;当轴向应变幅值大于10-3后,产生累积孔隙水压力。     

GSM-R无线通信消息认证方案研究

GSM-R作为铁路专用的通信技术,正在世界铁路范围内得到越来越广泛地应用,推动着各国铁路行业的发展。分析了GSM-R移动通信系统中安全保密体系的特点,引入了防克隆机制、双向认证机制和认证五元组,通过在HLR上设计认证向量及其中的随机数字段与MILENA-GE加密算法,提高了防止恶意无线网络用户对合法列车用户进行克隆攻击的能力,通过设计认证令牌AUTN和采用＂挑战-应答＂机制,实现了列车用户与服务网络的双向认证,通过密钥协商确定周期更新的加密密钥和完整性密钥,提供更高的数据私密性保护。在此基础上进一步提出了基于用户信誉体系的快速认证方案,以减少越区切换时列控系统列车-地面之间认证过程对通信时延产生的影响,并对快速认证方案的时延开销以及用户信誉等参数的取值进行了深入地分析。     

Short-Term Traffic Flow Forecasting for Freeway Incident-Induced Delay Estimation

Freeway incidents not only threaten travelers’ safety but also cause severe congestion. Incident-induced delay (IID) refers to the extra travel delay resulting from incidents on top of the recurrent congestion. Quantifying IID would help people better understand the real cost of incidents, maximize the benefit-cost ratio of investment on incident remedy actions, and develop active traffic management and integrated corridor management strategies. By combining a modified queuing diagram and short-term traffic flow forecasting techniques, this study proposes an approach to estimate the temporal IID for a roadway section, given that the incidents occurs between two traffic flow detectors. The approach separates IID from the total travel delay, estimates IID for each individual incident, and only takes volume as input for IID quantification, avoiding using speed data that are widely involved in previous algorithms yet are less available or prone to poor data quality. Therefore, this approach can be easily deployed to broader ranges where only volume data are available. To verify its estimation accuracy, this study captures two incident videos and extracts ground-truth IID data, which is rarely done by previous studies. The verification shows that the IID estimation errors of the proposed approach are within 6% for both cases. The approach has been implemented in a Web-based system, which enables quick, convenient, and reliable freeway IID estimation in the Puget Sound region in the state of Washington.     

关于设置平面交叉口直行待行区的思考与实践

在机动车保有量迅速增长的今天,交叉口通行效果在区域道路运行状况中扮演着日益重要的角色,使其逐渐成为交通矛盾的中心。为进一步缓解交通压力,上海市公安局交通警察总队于2010年3月起在本市增设了19个交叉口直行待行区,使全市拥有直行待行区的路口总量达到23个。出发点在于总结近年来设置待行区的实践经验,着眼于优化世博后城市交通,结合世博大客流交通压力下的实际运行状况,为进一步提高平面交叉口的资源利用率探索理论规则。通过初步分析直行待行区的适用条件和设置方法,并以一个典型的直行待行区路口为例,对设置前后的交通效益指标进行对比。结果表明:合理设置机动车直行待行区可以缩短周期时长,减小平均延误,提高进口车道的资源利用率。     

基于遗传算法的交通信号优化控制研究

通过对信号交叉口延误模型的研究,提出了一种新的相位配时优化算法。此算法是将遗传算法引入到延误模型中,以信号交叉口车辆的平均延误最小为目标,考虑交叉口服务水平等多方面的限制,建立新的模型算法,并将其应用于常州市的典型交叉口,获得较好的优化结果。