Evolving role of models in transport planning

Abstract

The recent profound change in the role and basis of the UK National Road Traffic Forecast and the current efforts to develop a more policy-oriented National Transport Model are described. The role of models which seek to represent aspects of travel behaviour in detail, and are used for detailed design of schemes and policies, is contrasted with that of simplified strategic models which lay people and professionals can use to test policy options and identify the most promising ones. The paper explores the role and reputation of models in the transport planning process and suggests that models are more often used to justify than to challenge predetermined policies; model predictions which conflict with orthodox policy, or with the analyst's intuition, are generally accepted most reluctantly. A model's popularity is likely to have more to do with its presentation, interface and pedigree than its accuracy or track record. More sensitivity analysis of model coefficients and input parameters is needed.

Keywords:

• transport demand
• models
• policy