Railway vehicles are fitted with coned wheels to provide a measure of stability, but it can be shown that since the forces between wheel and track are non-conservative, dynamic instability occurs at a certain critical speed. Under these conditions the wheelsets sway from side-to-side of the, track with the flanges of the wheels contacting the rails. This can lead to derailment when the wheel climbs up the rail and eventually jumps off. The forces which exist between wheel and rail are due to the phenomenon known as "creepage", and various theories exist which predict these forces in the plane of the contact area. An investigation has been carried out into these theories with the railway wheelset problem in view, particularly the flange contact case. It is possible, by assuming small displacements which avoid flange contact, to carry out a linearised study of the lateral dynamics of a wheelset, but the presence of the wheel flanges introduces a nonlinearity into the problem. A mathematical model of a wheelset and track has been defined based on real wheels with a "worn" tyre profile and real track. Computer programs have been written which calculate the contact points when the wheelset is displaced laterally and yawed by various amounts, including flange ,contact conditions. Up to three contact points can exist between the wheelset, and track. Forces in the contact areas have been calculated using the various theories assuming the wheelset to be rolling along the track a ta constant velocity in a displaced position. These forces have been manipulated to give the total forces and, moments on the wheelset and are presented for various vertical load distributions and for various angular and lateral displacements of the wheelset from its central position. Although theories exist which predict the forces for flange type contact, i. e. very elongated contact ellipse with a large amount of spin present, it became apparent during the course of the investigation that very little experimental evidence was available for such conditions. As a result a roller rig was built to provide this data, and measurements were made of the lateral force due to various amounts of lateral creep and spin on elongated contact ellipses. Results from these tests have been compared with the available theories and show reasonable agreement.

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Accurate measurement of a vehicle's resistance to motion on a road (the 'road load'), and the separation of this resistive force into its contributory components is of fundamental importance to generate the data required for vehicle performance assessment, the calibration of a modem chassis dynamometer and for comparing the drag of different vehicles or vehicle configurations. Established methods of determining road load on a test track are the coastdown and steady state torque tests, but environmental variability (largely due to ambient wind) and differences in the vehicle operating conditions cause wide variation in the results. This thesis describes a comprehensive study into methods of acquiring and analysing road load data at a test track. A mathematical model of the vehicle travelling in a straight line, in the presence of ambient wind, is developed and may be applied to measured data obtained in both the coastdown and the steady state test modes. The model includes the aerodynamic drag, tyre losses, transmission and un-driven wheel losses and the variation of aerodynamic drag with yaw angle. Experimental data obtained at a test track, using advanced instrumentation (including on-board anemometry and wheel torque meters) are analysed to obtain estimates of the coefficients in the road load equation. The results from an initial study demonstrate the importance of measuring the local wind at the test vehicle and the transmission losses if the total drag is to be accurately measured and separated into its contributory components. The coastdown method is shown to be more accurate and repeatable than the steady state method, and is therefore used as the basis of an advanced test procedure. Up to four coefficients can be determined from the coastdown data using a parameter optimisation routine. This routine fits the mathematical model to the measured coastdown profile to obtain estimates of the road load coefficients including the variation of aerodynamic drag coefficient with yaw angle. Results using this analytical method show that all four coefficients can be determined from coastdown data if there is sufficient ambient wind, and hence lay the basis for an advanced test method using only data from track tests. Constrained methods, where one or more of the parameters is fixed, can be used to investigate a single source of drag. The reduction in the total number of tests required to achieve an acceptable level of accuracy in the variable coefficients when using the constrained method is demonstrated.

This research develops a conceptual model of freight modal choice in which the basic unit of analysis is the socio-organisational group. Research into freight modal choice at the level of the firm has tended to disregard the nature of human choice and to assume that modal choice can be explained in terms of technological phenomena or cost relationships. There is also a tendency to equate the modal choice of organisational members with the modal use of firms. The approach adopted in this work is to accept that there are different interest groups within shipper firms and that such groups may not necessarily form a consensus of opinion about freight model choice. It is assumed that different socia-organisational groups may form different implicit theories about transport systems. Such an approach is called the social perceptual approach. The conceptual modal is converted into an operational model and an empirical investigation is undertaken into the area of modal choice between air freight transport end surface less than full load freight transport from the United Kingdom to Western Europe. In particular, the standpoint of shipping managers (managers responsible for arranging international freight transport in exporting companies) is examined vis-a-vis certain normative approaches such as the through transport concept.