Static and Dynamic Stability of Unsymmetric Two-Axle Railway Vehicles Possessing Perfect Steering

For railway vehicles having coned wheels mounted on solid axles, there is a conflict between the stability of lateral deviations from the motion along the track and the ability to steer round curves. A general theory is developed for the two-axle vehicle in which there is a lack of symmetry, fore-and-aft, both of the interwheelset structure and of the equivalent conicities of the wheelsets. It is shown that whilst parameters can be selected which provide static and dynamic stability and perfect steering for both directions of motion, there is a lightly damped mode of oscillation for any practical configuration and the significance of this is discussed.     

Economics of regulation in shipping

In this paper the author explores the nature and scope of social regulation in shipping comparing its nature with that of economic regulation per se. Whilst economic regulation affects liner shipping only, social regulation—impelled by a specific concern for health and environmental protection, rather than a desire for optimal resource allocation—effects all types of shipping. The legislation emerging from this has had important (and often overlooked)economic impact; focusing on the conditions, under which a carrier discharges his duties, these regulations may determine, to a greater or lesser degree, the levels of cost and service. He concludes that, whilst the concept of social regulation has a valid, humanitarian base, the cost of its implementation should not be underestimated.     

Optimal Control of the Tractor-Semitrailer Truck

This paper is concerned with the braking performance and the handling behavior of the tractor-semitrailer truck under optimal braking. Optimal control theory is used in order to deal with the problem and a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve it numerically. Results for some chosen braking maneuvers are obtained for a nonlinear truck model which has 14 degrees of freedom. These results show that, for the chosen maneuvers an idealized anti-skid braking is close to being optimal in the sense defined in this paper. Implementation of an idealized anti-skid braking on the tractor-semitrailer truck, however, may be not desirable.     

Approximate algorithms for the discrete network design problem

The discrete network design problem is one of finding a set of feasible actions (projects) from among a collection of possible actions, that when implemented, optimizes some objective function(s). This is a combinatorial optimization problem that is very expensive to solve exactly. This paper proposes two algorithms for obtaining approximate solutions to the discrete network design problem with much less computational effeort. The computational savings are achieved by approximating the original problem with a new formulation which is easier to solve. The first algorithm proposed solves this approximate problem exactly, while the second is even more efficient, but provides only a near-optimal solution to the approximate problem. Experience with test problems indicates that these approximations can reduce the computational effort by a factor of 3–5, with little loss in solution accuracy.     

The changing structure of the UK port industry and its impact on stevedoring costs

This paper examines the impact the changing maritime technology has had on the structure and development of the UK port transport industry. In particular, it describes the major institutional changes that have occured in response to technological and other developments and the influence these have had on the cost structure of individual stevedoring operators. Finally, it describes the resultant pricing policies adopted by stevedores and concludes that these have been exacerbated by the failure of successive governments to adopt sound and consistent policies towards the industry.     

Light rail transit in Canada

This paper describes current light rail transit planning and operation in Canada's major cities and smaller communities. There are ten urban areas in Canada with 250,000 or more people. Two of these have light rail systems in operation, three have lines under construction and nine others are planning LRT systems.     

An analysis of the commuter departure time decision

Transportation planners and transit operators alike have become increasingly aware of the need to diffuse the concentration of peak period travel in an effort to improve gasoline economy and reduce peak load requirements. An evaluation of the potential effectiveness of strategies directed to achieve this end requires an understanding of factors which affect commuter trip timing decisions. The research discussed in this article addresses this particular problem through the development and estimation of a commuter departure time (to work) choice model.A number of conclusions were drawn based on the departure time model results and related analyses. It was found that work schedule flexibility, mode, occupation, income, age, and transportation level of service all influence departure time choice. The uncertainty in work arrival time and the consequences of various work arrival times may also be determinants of commuter departure time choice.The estimated model represents improvements over previous work in that it more explicitly considers work arrival time uncertainty and travelers' perceived loss associated with varying work arrival times, and additional socio-demographic factors which can potentially affect departure time choice. Furthermore, the estimated model includes consideration of transit commuters, in addition to single occupant auto and carpool work travelers. The inclusion of transit commuters represents a particularly important contribution for policy analysis, since the model could potentially be used to study the effect of service and employment policies on transit system peak load requirements.     

Effects of Operational and Design Parameters on the Sequence of Locking of the Wheels of Tractor-Semitrailers

It is known that loss of directional stability during braking occurs in many road accidents involving tractor-semitrailers. To minimize the undesired directional response, the correct order of locking of the wheels is of importance and should receive greater attention. This paper examines the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers. The way in which the correct locking sequence may be achieved is also discussed in detail.     

Perceived and actual costs of operating cars

The perception that drivers have of car operating costs is an important factor in determining modal split characteristics. Theoretical figures derived from discriminant analysis models suggest that drivers perceive only petrol costs, but this has not been cor roborated by detailed surveys. This report examines in detail perceived and actual journey to work petrol costs of a sample of London commuters. The perception is also examined of related factors, such as petrol consumption and distance, in an attempt to throw some light on the perception mechanism itself.