Modelling

Computer models of the transport system are likely to be required to provide the information necessary for an appraisal that complies with the Government’s New Approach to Appraisal. These models may take a variety of forms, depending on the nature of the study area, the problems to be addressed and the potential solutions to be considered. The availability of existing models and data may also influence the form of the model adopted in any particular study. In most Multi-Modal Studies, the appropriate model structure will include separate representations of the highway and public transport system along with some means of forecasting the changes in demand over time and between modes. In some studies, it may also be appropriate to extend the traditional transport-modelling framework to include the impacts of transport on land uses.

Key Entry Points:

Introductory Material

An Introduction to Transport Analysis, (TAG Unit 1.1) provides an introduction to the principles of transport appraisa.l

Guidance for the Project Manager

The Overall Approach: Steps in the Process ( TAG Unit 2.1) presents a flow diagram applicable to a range of transport studies that involve appraisal. The flow diagram shows where modelling fits into the process.

Summary advice on modelling ( TAG Unit 2.4) introduces the models that are used in the appraisal process.

Guidance for the Expert

Modelling (TAG Unit 3.1) describes the transport and other models that the specialist user is likely to require.

A full list of TAG Units is available on the Documents page.

For further information:

Major Scheme Appraisal in Local Transport Plans Part3, Detailed Guidance on Forecasting models for Major Public Transport Schemes provides guidance on the modelling approach the Department expects for the appraisal of LRT and Guided Bus Schemes. This provides procedures on forecasting purely for public transport scheme appraisals. Part 3 is currently being revised. See Appraisal Links.

Further information on modelling is available on the DfT website; see Appraisal Links.