This article describes the traffic forecasting procedures used for Japanese urban and inter urban tolled motorways and discusses some attempts to improve these. The traffic forecasting procedure for motorways is a conventional aggregate sequential trip generation, distribution and diversion/ assignment model system based on the national travel survey. Major problems and limitations of this procedure are presented and discussed with special attention given to: (a) forecasting efficiency (ease of use, and the time and cost involved in obtaining an accurate forecast); (b) forecasting accuracy; and (c) the difficulties in obtaining forecasts which are relevant to particular traffic policy. Methods used to improve the motorway traffic forecasts are then presented. These include: (a) improvement of the diversion curve by segmentation based on either trip length, or by time of day; (b) the application of aggregate logic type diversion curves and (c) the application of a vehicle based disaggregate logit type route choice model.
Samenvatting