The allocation of buses in heavily utilized networks with overlapping routes

Many transit systems outside North America are characterized by networks with extensively overlapping routes and buses frequently operating at, or close to, capacity. This paper addresses the problem of allocating a fleet of buses between routes in this type of system; a problem that must be solved recurrently by transit planners. A formulation of the problem is developed which recognizes passenger route choice behavior, and seeks to minimize a function of passenger wait time and bus crowding subject to constraints on the number of buses available and the provision of enough capacity on each route to carry all passengers who would select it. An algorithm is developed based on the decomposition of the problem into base allocation and surplus allocation components. The base allocation identifies a feasible solution using an (approx.) minimum number of buses. The surplus allocation is illustrated for the simple objective of minimizing the maximum crowding level on any route. The bus allocation procedure developed in this paper has been applied to part of the Cairo bus system in a completely manual procedure, and is proposed to be the central element of a short-range bus service planning process for that city.     

Planning school transport: design of routes with flexible school opening times

Abstract

This paper puts forward a methodology for designing a system for school transport which, apart from designing routes, specifies school opening times. Traditionally school opening times have always been identical in the same area meaning many buses have to be used at the same time. This paper suggests the staggering of school opening times in order to minimise the number of buses and thereby reduce the enormous costs involved in running them. The methodology is based on: a first phase which addresses the classic routing problem by using mixed integer lineal programming and a second phase which uses bi-level programming to find the vector for school opening times, which, when staying within the constraints of the problem, minimises the direct costs of the system. The upper level represents the evaluation of the system costs and the lower level finds the best combination of optimum routes for the same bus.     

A study of travel time and reliability on arterial routes

This study is concerned with travel time and operational reliability on arterial routes. Reliability is viewed in terms of the consistency of operation of the route under investigation and defined in terms of the inverse of the standard deviation of the travel time distribution.Under certain assumptions, travel time behavior on an arterial route is seen to closely follow a gamma distribution; the reliability measure can be derived accordingly. Utilizing arterial travel time data from the Chicago area, both a regression and a statistical model are show to serve as efficient techniques in predicting reliability. The prediction models are evaluated.     

The planning of urban bus routes and frequencies: A survey

Urban bus services still play an important role in the movement of people in Britain, although since the 1950's bus patronage has been declining and costs of operation have been increasing. Most of the urban bus networks in Britain (and to a very large extent the Western World) have developed or evolved over the years and it is sometimes said that, despite the changing conditions of bus transport, few of these bus networks in Britain have undergone major re-organisation. A survey was carried out to ascertain this view and to establish the approaches used by British urban bus operators.Five approaches to the planning of urban bus routes and frequencies have been identified: (1) manual; (2) Market Analysis Project; (3) systems analysis; (4) systems analysis with interactive graphics; and (5) mathematical. Previous research in, and application of, the different approaches are described and examined.Between 1970 and 1980, 82.4% of those British urban operators who responded to the survey carried out some kind of major bus study. The survey results run counter to the view that there has been little recent change in urban bus networks in Britain, but the alleged conservatism of the bus industry appears when the approaches used for re-planning bus services are examined - 71.4% of the operators used a manual approach and only a meagre 28.6% made use of simple assignment techniques to predict the potential passenger impacts of the alternative networks appraised.     

The planning of aircraft routes and flight frequencies in an airline network operations

This research is aimed at developing a model that maximizes system profit when determining the aircraft routes and flight frequencies in a network. The model employs network flow techniques to effectively collect or deliver passenger flows from all origins to all destinations using non‐stop and multi‐stop flights in multi‐fleet operations. The model was formulated as a multi‐commodity network flow problem. A Lagrangian‐based algorithm was developed to solve the problem. To test the model in practice, a case study is presented.     

The effects of planned and unplanned transfers on public transport users' perception of transfer routes

Many authorities are investing in new infrastructure to improve the quality of public transport (PT) services in the hope to increase mode switch from cars. The goal is to provide users with an integrated multimodal PT network by facilitating transfers. There exists a lack in the clarity of the attributes which defines a planned transfer and the effects of planned transfers on users' willingness to use routes with transfers. The present study provides approximate effects of ‘planned’ and ‘unplanned’ transfers on PT users' decisions to use transfer routes. The study focuses on two attributes of ‘planned’ transfers, integrated physical connection of transfers and information integration. A user preference survey was undertaken in Auckland, New Zealand. Analysis of the results shows that physical integration is more important than information integration for current PT users. Results also suggest that information integration has a greater influence on users of transfer services which are more closely aligned to being ‘unplanned’.     

Urban delivery industry response to cordon pricing, time-distance pricing, and carrier-receiver policies in competitive markets

The paper develops a set of analytical formulations to study the behavior of the urban delivery industry in response to cordon time-of-day pricing, time-distance pricing, and comprehensive financial policies targeting carriers and receivers. This is accomplished by modeling the behavior of receivers in response to financial incentives, and the ensuing behavior of the carrier in response to both pricing and the receivers’ decisions concerning off-hour deliveries. The analytical formulations consider both the base case condition, and a mixed operation with both regular hour and off-hour deliveries; two pricing schemes: cordon time of day, and time-distance pricing; two types of operations: single-tour, and multi-tour carriers; and three different scenarios in terms of profitability of the carrier operation, which include an approximation to the best case, the expected value, and the worst case. The analyses, both theoretical and numerical, highlight the limitations of pricing-only approaches. In the case of cordon time of day pricing, the chief conclusion is that it is of limited use as a freight demand management tool because: (1) in a competitive market the cordon toll cannot be transferred to the receivers as it is a fixed cost and (2) the structure of the cost function, that only provides an incentive to the carrier to switch to the off-hours when all the receivers in the tour switch to the off-hours. The analyses of time-distance pricing clearly indicate that, though its tolls could be transferred to the receivers and provide an incentive for behavior change, the magnitude of the expected toll transfers under real life conditions are too small to have any meaningful impact on receivers choice of delivery times. In essence, the key policy implication is that in order to change the joint behavior of carrier and receivers, financial incentives—or programs that foster unassisted off-hour deliveries—should be made available to receivers in exchange for their commitment to do off-hour deliveries. As the paper proves, if a meaningful number of receivers switch to the off-hours, the carriers are likely to follow suit.     

带隔板并联管组流量分配特性的数值模拟

文中提出一种隔板分流方法,以改善并联管组流量分配的均匀性。建立带隔板和无隔板的并联管组的几何模型和数值模型,通过数值计算,确定了最佳隔板设置方法,研究了集管直径、支管直径、进口流速和支管间距对流量均匀性的影响。结果表明:隔板分流可减小各支管流量比的均方差,可减至无隔板分流的1/3,增加并联管组流量分配的均匀性;大集管、小支管的并联管组均匀性较好;进口流速较小时,各支管流量更均匀;支管间距对流量均匀性的影响很小。     

论打造广西特色治超执法新模式的必要性和意义

文章针对广西治超执法情况的特点及存在的主要问题,分析了新形势下进行广西治超新模式改革的必要性,介绍了广西公路部门实施的治超执法新模式和手段,总结了广西特色治超执法模式改革取得的成绩。     

防喘阀开启时的压缩机工作特性研究

为研究防喘阀开启状态下的压缩机工作特性,结合压缩机防喘阀开启的机理,分析了在防喘阀开启状态下的压缩机入口流量、入口汇管流量和防喘阀开度的变化规律。并在此基础上分析了调节转速对压缩机的影响。研究结果表明:防喘阀开启后,入口汇管流量和防喘阀开度随着时间有规律地波动;入口流量不变且等于防喘振流量;降低转速,防喘阀开度先增大,后减小,稳定后比初始开度小;增加转速,防喘阀开度先减小,后增大,稳定后比初始开度大。     

基于XPS板隔热层的多年冻土区路基温度特性分析

针对XPS板隔热层在多年冻土区路基中应用的适宜性展开研究,分析了XPS板路基形式的温度随深度、宽度和时间的变化情况。结果表明:各个测点的地温年变化近似均呈现正弦分布形式,且地温周期大致相同;各个测点的全年温差随深度增加均减小,可推断出活动层厚度;路基横断面对称位置处呈现不对称性,可能导致路基的不均匀变形。研究成果可进一步为类似工程提供依据。     

交通现代化的内涵和特征

本文梳理了现代化内涵和交通现代化的研究成果。作者提出从静态角度,交通现代化是交通运输的一种状态,它最大限度的、经济地克服了时空对经济活动的约束;动态角度,交通现代化实质上是空间上的时间距离不断缩短、费用距离不断下降的过程。本文指出快速与经济是现代交通运输的两大基本特征,并且在新一轮科技革命和产业革命背景下交通越来越与其他功能或要求融合一体。基于现代交通运输的内涵,我国应构建高速交通网,发展交通一体化,推进物流降本增效。     

专业货运机场的量化界定与空间特征

当前,由于专业货运枢纽机场的缺乏,我国航空物流及其相关产业的发展都面临着较大瓶颈。根据全球专业货运机场发展经验分析,"第三方物流企业/电商平台+中小城市"的航空货运枢纽建设是我国未来民航业发展的必然趋势和重要组成,也是建设民航强国、培养具有国际竞争力的优秀企业和明星城市的必由之路。本文通过分析欧美各类型货运枢纽机场,结合我国现状,提出专业货运机场量化界定和空间差异化特征,为我国专业货运机场及其临空范围的空间规划建设提供参考。     

φ900mmT/R射流风机的特点及其应用

本文主要介绍沈阳-本溪高速公路大峪、吴家岭隧道引进的英国Matthews&Yates公司设计制造的φ900mmT/R射流式隧道风机技术原理、性能指标、主要结构特点和技术措施、投资额及应用情况.结果表明,引进的φ900mmT/R射流风机是成功的,各项技术性能达到国内外同类机型的先进水平,尤其在动力性和经济性方面居领先地位.     

Modeling NOx and NO2 emissions from mobile sources: A case study for Hamilton, Ontario, Canada

This study characterizes the dispersion of emissions of oxides of nitrogen and nitrogen dioxide from traffic sources in the Hamilton census metropolitan area. The Integrated Model of Urban Landuse and Transportation for Environmental Analysis software was used to estimate emissions of oxides of nitrogen from traffic sources. The Air Pollution Model, was used to simulate dispersion of the traffic emissions over the city. The models account for the two primary wind directions in this region – the prevailing southwest and a secondary northeast direction. The results show a prominent triangle of high pollution defined by major roads and highways along the periphery of the Hamilton Harbour, at peak-hour. With southwest winds, residential areas along the northern shoreline of the Harbour are affected, while the western sections of the city are affected by northeast winds. High concentrations are persistent in some areas, for both wind directions. The resulting dispersion surfaces characterize the spatial distribution of traffic emissions and thus provide a means of assessing population exposure over the Hamilton area.     

高温高压疲劳储能容器的设计与制造

文中介绍了设计压力为20 MPa、设计温度为400℃、工作压力波动范围为0~18 MPa、工作温度波动范围为常温~375℃的高温高压疲劳储能容器的结构设计及有限元应力计算与评定。规定了储能容器所需采购的钢板、锻件及焊接材料的质量控制计划。制定了储能容器制造所需的原材料复验、焊接方法、无损检测、产品试件及焊后热处理的技术要求,按此技术要求制造的储能容器满足工艺需求并顺利通过了检查和验收。     

我国货运功能为主的机场界定及特征分析研究

随着社会对货运机场的关注度越来越高,国家也提出要研究以货运功能为主的机场布局及运行机制,但目前对其概念界定和特征缺乏分析和研究。本文从国内外研究出发,结合国内实际,提出货运功能为主的机场定义,并对国内外机场进行研判;通过分析国外类似机场,结合实际情况,从机场本身物理特性、功能及其发展模式等方面提出货运功能为主的机场主要特征,以期为行业管理部门决策和相关学者研究提供参考。