Dynamic Interaction between Wheel and Track - A Parametric Search towards an Optimal Design of Rail Structures

The dynamic vertical interaction between a moving rigid wheel and a flexible railway track is investigated. A round and smooth wheel tread and an initially straight and noncorrugated rail surface are assumed in the present optimization study. A symmetric linear three-dimensional beam structure model of a finite portion of the track is suggested including rail, pads, sleepers and ballast with spatially nonproportional damping. The full interaction problem is numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the track. Transient bending stresses in sleepers and rail are calculated. The influence of seven selected track parameters on the dynamic behaviour of the track is investigated. A two-level fractional factorial design method is used in the search for a combination of numerical levels of these parameters making the maximum bending stresses a minimum.     

Citizen participation through communicative action: Towards a new framework and synthesis

The record of public involvement in the transportation planning process in the United States has been uneven and, at times, disappointing. It is therefore a matter of some satisfaction that the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), recognizes that public involvement and input is essential in transportation plan-making. However, little guidance is available to planners as to how participatory democracy could possibly be enhanced and improved in the existing transportation planning process. As matters stand today, the predominant use of technical rationality in the planning process, to the exclusion of communicative action, has probably been the biggest problem. This paper introduces the concepts of communicative action to buttress and complement technical rationality, currently used in the transportation planning process. A real-life case-study is presented to demonstrate how communicative action was successfully used in a problem-ridden planning situation. Validity claims as suggested by Habermas in his Theory of Communicative Action are used in this case-study. It is concluded that academic institutions as well as planning agencies will have to make a concerted effort to educate and train planners not only to be involved with the engineering of our infrastructure, but also to be equally concerned with coping with the social, economic and political dimensions of planning.     

Cost benefit analysis of urban minibus operations

Earlier work by the Transport Studies Group of the Polytechnic of Central London on minibus development in Britain for the Transport and Road Research Laboratory provided a financial analysis of intensive urban minibus operation. This is taken as the basis for the application of cost-benefit analysis. Unit operating cost savings and passenger benefits are taken into account, using typical demand elasticities derived from earlier work. Particular attention is paid to the problem of evaluating passenger benefits for which waiting time at the roadside is not necessarily an adequate proxy. A direct survey of passenger waiting times indicates that these do not necessarily decrease when a higher-frequency minibus service replaces a conventional bus service but the improved convenience produces an increase in ridership which may be assessed in terms of a demand curve shift to estimate benefits obtained.     

Merchant fleet development by legislation: lessons from West and Central Africa

In the late 1960s and early 1970s, several developing maritime nations began to invoke their 'legitimate right' to carry, in their own vessels, cargo generated by their own import and export trades as one way to reverse their underdevelopment and dependency on traditional maritime nations. Consequently, they embarked on the establishment and development of national merchant fleets by means of cargo reservation legislation and flag discrimination practices. West and Central African states have pursued a vigorous policy of merchant fleet development for over two decades. This study examines some of the cargo reservation policies and flag discrimination practices in West and Central Africa and concludes that these two measures alone are insufficient to build up a significant merchant marine. Merchant fleet development depends equally on the resolution of problems such as shortage of ship finance or capital, disruptive bureaucratic politics among the state agencies concerned with shipping, low volume of trade, and contradictory and ambivalent fiscal and macroeconomic policies in these countries that impede the development of the maritime sector.     

A schedule-based time-dependent trip assignment model for transit networks

A schedule-based time-dependent trip assignment model for transit networks is presented. First the transit network model is formulated using the schedule-based approach, in which the vehicles are assumed to arrive punctually in accordance with a scheduled time-table. Based on a previously developed time-dependent shortest path algorithm, an all-or-nothing network loading procedure is employed to assign the passenger trips onto the network. Both the passenger demand and scheduled time-table are time-varying. This provides a versatile tool for the evaluation of the performance of transit networks subject to peak period loading. A case study using the Mass Transit Railway System in Hong Kong is given to illustrate the potential applications of the model.     

CORADIA LIREX——创新的轻型区间快速动车组家族

ALSTOM LHB 公司在LIREX样车的基础上于2001年开发了CORADIA LIREX动车组家族.该动车组整列为低地板、有创新的传动设计以及符合旅客需要的车内布置及设施,为区间铁路运输列车提供了新的标准.模快化结构的车辆是按各种不同传动系统设计的,除牵引电动机外,所有传动部件均安装在车顶上.文章介绍该动车组的基本设计、电气部分、机械部分以及主要技术参数.     

A methodology for planning bus service

A methodology to assist transportation planners in designing bus services is developed. The methodology is most relevant for use in locations where bus service of the type being studied does not currently exist and therefore no information is available on past choice behavior, or in instances when transferability of travel models estimated in another location is difficult. The methodology assesses the sensitivity of bus service characteristics upon intended bus usage using survey data collected in Orange County, California, by the Orange County Transit District (OCTD). The methodology is based on a nonparametric statistical test developed by Kolmogorov and Smirnov.Scenarios describing hypothetical operations of bus service are presented to survey respondents who indicate their intended levels of bus usage under each situation. Significant differences between the response distributions associated with pairs of scenarios are identified and potential ridership levels, as bus operations become more favorable, are assessed. Various user segments are then identified on the basis of their levels of intended bus usage and the corresponding marketing implications associated with each segment are discussed.     

The Influence of Structural Flexibilities on the Straight-running Stability of Motorcycles

A new tyre model for studies of motorcycle lateral dynamics, and three new motorcycle models, each incorporating a different form of structural compliance, are developed. The tyre model is based on “taut string” ideas, and includes consideration of tread width and longitudinal tread rubber distortion and tread mass effects, and normal load variation. Parameter values appropriate to a typical motorcycle tyre are employed. The motorcycle models are for small lateral perturbations from straight running at constant speed, and include (a) lateral compliance of the front wheel in the front forks, (b) torsional compliance of the front forks, and (c) torsional compliance in the rear frame at the steering head about an axis perpendicular to the steering axis.

Results in the form of eigenvalues, indicating modal damping properties and natural frequencies are presented for each model. The properties of four large production machines for a range of forward speeds, and the practicable range of stiffnesses are calculated, and the implications are discussed.

It is concluded that typical levels of structural compliance in models (a) and (c) contribute significantly to the steering behaviour properties of large motorcycles, and their observed behaviour can be understood better in terms of the new results than of those existing previously. Some conclusions relating to optimal structural stiffness properties are also drawn.