ON COMBINING DISCRETE CHOICE AND ASSIGNMENT MODELS

In large scale model systems, assignment models for route choice within modes and discrete choice models for mode and destination choice are frequently combined. This raises several important issues, in particular with respect to the algorithms of assignment models used for scheduled services and the specification and estimation of discrete choice models. It also raises important questions related to assessment of changes in transport systems in terms of consumers' benefits. The main problem is that the "traditional" approach implies an inadequate treatment of schedule delay which becomes much more important for travellers' decisions when public transport services have low frequencies and timetable information is used to plan trips. In this paper we present a feasible method for combining route and mode choice in one model. In our opinion this combined model will overcome some of the problems. A combined model is more demanding with respect to computation than treating assignment and mode choice separately, but parallel computing will make it an interesting option for the future.