Discrete travel choice models are based upon the estimation of the parameters of a so-called travel utility, which in fact is a conditional indirect utility function. Accordingly, its form and properties are originated by the form and arguments of direct utility and by the type of constraints considered in the original consumer behaviour model. This travel utility is usually specified linear for each of many segments of the modelled population. Departures from linearity have arisen from either of two perspectives. One is to propose non-linear forms purely on analytical grounds, advocating flexibility and arguing that the linear form is just a particular case of non-linear ones, be it quadratic or Box-Cox. A second approach is to derive non-linear forms that include elements or terms that have a microeconomic meaning as the presence of income effect or the importance of total travel time within discretionary time. In this paper the second approach is taken by proposing a fairly general model of consumer behaviour including time assigned to activities and goods consumption as sources of an explicit direct utility, plus the corresponding money, time and technical constraints. The conditional demands for goods and activity durations are obtained, which leads to an explicit conditional indirect utility function that commands the discrete travel choice. This highly non-linear form is explored directly and through approximations, such that the different terms can be given interpretations that illuminate the empirical results. This approach is offered as an alternative to the purely analytical flexible forms proposed in the literature. For the covering abstract see ITRD E126595.
Abstract