Chapter 17 Traffic models for highway schemes

The most appropriate form of modelling technique for the development and appraisal of a proposed highway scheme will depend on its location, size and the presence of other competing modes of travel available. For a large-scale highway scheme within or close to an urban area, alternative travel choices are likely to exist and some form of multi-stage model may be required. For schemes where model completion is limited a simpler transport demand model coupled with a road traffic assignment model may be more appropriate. The degree of traffic simulation required (macro, meso or micro) will also need to be decided for the assignment stage and this will depend on the purpose of the modelling process and the outputs required together with the degree of congestion on the highway network.