Abstract
Theoretically, there is reason to believe that, in particular among homogeneous groups of households, travel budgets tend to constant through time, so long as overall time and money patterns do not change drastically. Moreover, the empirical results of travel-budget studies give no reason to abandon the concept of constant travel-budgets. To integrate it in conventional transport models is not easy, however. How to value time is one problem among other theoretical and practical ones still to be solved. The travel-budget approach may be useful to evaluate existing and develop new ways of modelling.