This paper presents a methodology for analysing non-home-based (NHB) trips, and shows how the conclusions of its analysis were implemented in APRIL, the strategic model developed for assessing congestion charging in London. The model is incremental, and aims to predict the changes in travel that result from generalised cost changes. NHB trips are classified, and the implications are considered of charges applied to the home-based (HB) and NHB movements for each class. Several aspects of an analysis of Greater London Travel Survey data are considered: (1) its general approach; (2) NHB trips associated with work and non-work related HB tours; and (3) a synthesis of the results. There is a fairly extensive mathematical discussion of temporal and spatial variations in the APRIL model. Although the method described here contains several ad-hoc assumptions, it has proved to be a practical way of handling the most important effects. The overall changes in NHB trips are linked to changes in HB movements. It has been possible to model a sensible variation by time of day. The admittedly crude spatial allocation of the change in total NHB trips usually ensures that the change will be concentrated in those areas most affected by the congestion charge.
Abstract