Abstract:
This paper presents an examination of traffic volumes on Sydney's western road
network before and after the opening of the Mays Hill to Prospect section of the M4
Motorway. The aim of the examination is to identify any possible traces of induced
traffic growth, or new motor vehicle trips generated in response to the quicker travel
times made possible by the increase in road capacity.
The data show that average daily volumes on the M4 Motorway and Great Western
Highway grew from just under 80,000 vehicle movements per day in 1991 to around
100,000 in 1992 after the new motorway section opened. Once business-as-usual
growth (3,000 vehicles per day), road traffic reassignment (7,000 vpd) and possible
mode shifting from the rail network (6,500 vpd) are taken into account, a residual
volume of around 3,500 is left. This is likely to be redistributed or induced traffic
growth.
Induced traffic growth has significant implications for the sustainability of urban
systems. These are discussed in tandem with a brief review of the debate that has
taken place around induced traffic growth.
