The relationships between increases in motorway capacity and declines in urban rail passenger journeys : a case study of Sydney's M4 Motorway and Western Sydney rail lines.

This paper examines the relationship between the addition of urban motorway capacity and declines in rail passenger journeys on parallel alignments. The research presented here forms part of a wider study that investigates outcomes from the expansion of urban motorway capacity in Sydney and the phenomenon of induced traffic growth. Induced traffic growth is defined as new and additional road traffic movements that occur in response to increases in road capacity. By increasing road capacity, congestion and travel times are reduced, making travel by car more attractive. This generates a rapid succession of changes in travel behaviour across the surrounding network including traffic reassignment, traffic redistribution, generated traffic and passengers switching from parallel rail and public transport services, or mode shifting. This last response is the focus of this paper. Together, all form part of the composite effect called induced traffic growth. (a) For the covering entry of this conference, please see ITRD abstract no. E213716.