Forced Steering of Rail Vehicles: Stability and Curving Mechanics

A forced steering rail vehicle employs linkages between.the carbody and wheelsets to force a more radial wheelset alignment. It is shown that the curve negotiation capability of forced steering trucks is significantly improved over conventional and self steering radial trucks. Parametric curves are presented showing angle-of-attack and lateral flange force as a function of steering gain parameters and truck bending stiffness. It is also shown that the forced steering concept can produce kinematic instability and severely reduced critical speeds for low conicities and creep coefficients. Analytic expressions are derived that illustrate how these kinematic instabilities can be avoided.     

The optimal dispatching of taxis under congestion: A rolling horizon approach

Taxis make an important contribution to transport in many parts of the world, offering demand‐responsive, door‐to‐door transport. In larger cities, taxis may be hailed on‐street or taken from taxi ranks. Elsewhere, taxis are usually ordered by phone. The objective of a taxi dispatcher is to maximize the efficiency of fleet utilization. While the spatial and temporal distribution of taxi requests has in general a high degree of predictability, real time traffic congestion information can be collected and disseminated to taxis by communication technologies. The efficiency of taxi dispatching may be significantly improved through the anticipation of future requests and traffic conditions. A rolling horizon approach to the optimisation of taxi dispatching is formulated, which takes the stochastic and dynamic nature of the problem into account. Numerical experiments are presented to illustrate the performances of the heuristics, taking the time dependency of travel times and passenger arrivals into account.     

选择铁路方式出行的阻碍因素综述

研究表明,即使铁路出行是最具有成本效益的出行方式,许多出行者仍然会选择其他出行方式。这表明选择铁路出行方式存在一些与费用无关的阻碍因素。本文对有关这些阻碍因素重要性的文献进行了综述,这些研究主要来自英国,但也有一部分来自于其他国家。共确认了37种不同的阻碍因素,它们可以被划分为＂刚性因素＂、＂柔性因素＂与＂互补性因素＂。出行者通常不会只考虑其中的单一阻碍因素,而是将这些阻碍因素看成一个整体,由此使得对最重要阻碍因素的确认十分困难。很多情况下,对于某一出行者来说,所有存在的阻碍因素都需要在出行方式转移之前解决。在思考不同阻碍因素的相对重要性后,对克服它们并实现其他出行方式向铁路转移的最有效措施提出了建议。这涉及主要的交通政策,因为它能够为有限的可利用资金确定目标市场,从而影响出行行为并提高出行方式的可持续性。     

Mathematical Models and Computer Simulation of Nitrogen Concentration Profiles in Pulse Ion Nitrided Layers

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The future for in‐vehicle information systems: The technology and its impacts

In‐vehicle information has an important social role to play in improving the efficiency and safety of travel by all modes. In this review, three generations of system are identified. The first generation consists of simple in‐vehicle units relying heavily on external data. The second generation has more sophisticated in‐vehicle units with colour TFT screens and DVD players for maps and entertainment. The third generation again makes use of external data, using the mobile phone network to download map sections and other data as and when required, thereby obviating the need for beacons and map CDs. For locationing, GPS (and/or Galileo, the European version of GPS) remains the favoured technology. Portable devices offering multi‐modal information could improve inter‐modal transport efficiency.     

解读车轮轴承

像当今汽车上许多零部件一样,车轮轴承已变得越来越可靠,以至于在没有出现故障前我们往往会忽视它。然而,了解故障原因,即使是老化的原因,对我们来说都是有意义的。     

The Philadelphia story: 1975

Fishneck, a small and isolated fishing community in the Chesapeake Bay area, has been characterized by low education levels, few suprafamilial organizations, and little participation in institutions outside the community. Community members have resisted proletarianization through barter, exchange, supplemental wage labour, fill-in work, and family mutual aid.

These patterns are changing as contact increases with the wider society. Leisure is identified as the strongest pull toward participation. Results of greater contact include a more positive image to outsiders, a sharpened sense of community and community boundaries, and greater participation in the educational, economic, and political arenas. Whether this community changes toward a small-town fishing hamlet depends first on moving from clan-based to community-based internal organization.     

Uncertain benefits: Application of Bayesian melding to the Alaskan Way Viaduct in Seattle

Uncertainty is inherent in major infrastructure projects, but public decision-making for such projects ignores it. We investigate the uncertainty about the future effects of tearing down the Alaskan Way Viaduct in downtown Seattle, using an integrated model of housing, jobs, land use and transportation, on outcomes including average commute times. Our methodology combines the urban simulation model UrbanSim with the regional transportation model. We assess uncertainty using Bayesian melding, yielding a full predictive distribution of average commute times on 22 different routes in 2020. Of these routes, 14 do not include the viaduct and eight do. For the 14 base routes that do not include the viaduct, the predictive distributions overlap substantially, and so there is no indication that removing the viaduct would increase commute times for these routes. For each of the eight routes that do include the viaduct, the 95% predictive interval for the difference in average travel times between the two scenarios includes zero, so there is not strong statistical support for the conclusion that removing the viaduct would lead to any increase in travel times. However, the median predicted increase is positive for each of these routes, with an average of 6 min, suggesting that there may be some measurable increase in travel time for drivers that use the viaduct as a core component of their commute.     

Variances and covariances for origin-destination flows when estimated by log-linear models

An expression is derived for the variances and covariances of the logarithms of origin- destination flows when estimated by one of a family of log-linear models. Among this family is the Furness growth factor model, the gravity model, the Willumsen model and the Van Zuylen-Bell model. Variances and covariances for the logarithms of the parameters incorporating prior information and for the values of the constraints with which the fitted values must conform are transformed linearly into approximate variances and covariances for the logarithms of the fitted values. Additional error due to misspecification of either the model or the constraints is not taken into account. Depending on the model, the prior information parameters may correspond to values of a deterrence function or to a base year trip matrix, while the constraints may represent design year trip end totals or traffic counts. As an illustration, the expression is applied to an example involving Willumsen's model.