ABSTRACT
Traffic forecasts must always depend on a very wide range of what we might call exogenous or external factors. For each of these factors depending as they do on the national and local economy, planning decisions, public and private investment, etc., a shared set of forecasts has to be developed. This chapter frames the choice which this traffic faces which defines whether this traffic will choose to use the target infrastructure or whether it will use the competing alternatives. On many occasions the first basis for the definition of this In-Scope traffic will be a traditional network model. In network model the analysis of traffic assignment will be carried out within one of the transport modelling packages. Up until now relying on the approach commonly adopted in the traditional network modelling approach our analysis has commonly rested on the assumption that drivers make their assumptions on the basis of the actual time it will take them to transit the system.
