ABSTRACT
Two principal limitations affect an individual's travel behaviour. First, travel demand, unlike the demand for other commodities, is a 'derived demand'; travel is normally demanded not for its own sake but as a means of consuming some other good or service. A trip may be made because a household member wishes to buy commodities or service or to obtain other satisfactions (e.g. to purchase food, to visit friends, to earn income). Second, in the short run the travel decisions of the individual are subject to his residential location, workplace, car ownership or availability , and the availability of various modes at his residential location. However, in the long run factors such as location and car ownership are also decision variables. Furthermore, the attributes of the transport system may influence these decisions. Conventional demand modelling has treated travel demand and locational decisions as independent phenomena, at least in the sense that there is no feedback from one to the other. Consequently, it has been impossible to provide reliable forecasts of the effects of changes in transport system attributes on travel demand, without taking into account at the same time the effects of changing location.
