Presentational issues in the analysis of motorists' stated preference route choice data

The most common areas of Stated Preference (SP) application are to choice contexts which do not yet exist or where the attribute variation is far from ideal for Revealed Preference (RP) modelling. Although tolled routes and crossings exist, all drivers within a specific road user category face the same toll and hence its effect cannot be disentangled from any route specific effects. The variations across routes in petrol cost in particular and to a lesser extent journey times are typically poor from a choice modelling perspective. Primarily for these reasons, but also because of the lower unit costs of data collection, SP has been widely employed in the context of new tolled roads and facilities. The move to the private financing of new infrastructure centred around competitive tendering has also provided a stimulus to such studies. Many of these motorists route choice SP applications are routine in nature, offering trade-offs between time and toll with petrol cost and other variables, such as road surface or some representation of reliability, on occasions making an appearance. Relatively little attention has been paid to methodological issues such as the functional form of behavioural response, the nature of SP responses in what is a contentious choice context, the impact of different means of presentation, and the realism of the choice task.As part of a study conducted for the UK Department for Transport and centred around the new privately financed M6 Toll Road in the West Midlands area of Great Britain, over 3200 motorists completed SP exercises that explored a number of interesting and important methodological issues. For the covering abstract see ITRD E137145.