The crisis for transportation planning modelling

The paper considers the performance of land‐use transportation study techniques over the past ten years. Although primarily viewed from a U.K. perspective the paper reviews matters of principle which are of international relevance. The changing context and tasks for modelling are reviewed and the current role and applications of such models considered. The capability of established models to meet these changing requirements is examined. Attention is drawn to model specification and the ability of models both to represent new policies and to predict traveller responses to them. Also relevant is the ‘behavioural’ theme and the way in which survey technique conditions the data obtained.

Particular emphasis is placed on the accuracy of modelling, both in the representation of base year travel patterns and in the forecast mode. The inherent uncertainty concerning input data is discussed and the frequent failures to establish model validity are noted.

Three crises for U.K. transportation planning practice are identified: the ageing of data bases, the accuracy and validity of models and the current changes to the institutional context of transport planning in the U.K. Some potential remedies for the first two difficulties are proposed. It is concluded that only the last ‘crisis’ represents a real threat to the application of rational methods in transportation planning.