The issue of generated traffic and the view that new roads can generate additional traffic has long been in the minds of those involved in transport planning practice. In December 1994 the Standing Advisory Committee on Trunk Road Assessment (SACTRA) report on induced traffic was published. In the interim stage and until further evidence is gathered, induced traffic attributed to the construction of new highway schemes may be determined by elastic assignments. Variable matrix economic assessment has been recommended by SACTRA and has also been endorsed by the Department of Transport. This paper describes a method where elastic assignments were performed to estimate the likely amount of induced traffic on likely amount of induced traffic on a section of a proposed highway scheme. The overall approach is in line with recommendations made by SACTRA involving elastic assignment techniques and the use of higher tier models. The method was based on iterative elastic assignments where the forecast model networks with the scheme were subjected to unlimited growth in future years until the benefits over the networks without the scheme dissipated. Economic assessment based on variable matrix methods were performed. The paper tables the difference in benefits obtained under fixed and variable matrix economic assessment.
Abstract