Congestion relief and public transport: An enhanced method using disaggregate mode shift evidence

Abstract

Mode shift from public transport (PT) to private car in the event of PT withdrawal can increase the level of traffic congestion in urban areas. This increase in congestion is interpreted as the congestion relief impact associated with urban PT. However, existing methods for estimating the impact of PT on relieving traffic congestion have generally assumed a fixed mode shift to car. This paper presents an enhanced method for estimating the congestion relief impact of PT by varying the mode shift to car. First, primary data from a survey conducted in Melbourne, Australia was used to develop a linear regression model for predicting the share of mode shift from PT to car. The Victorian Integrated Survey of Travel and Activity (VISTA) dataset was then applied to this model to estimate the potential mode shift for different spatial areas of Melbourne. Second, PT congestion relief impacts were estimated by contrasting the level of congestion in two scenarios: ‘with PT’ and ‘without PT’. This stage was undertaken using the Victorian Integrated Transport Model (VITM), a conventional four step model. The results show that PT operations in Melbourne contribute to reduce the number of severely congested links by more than 63%. Vehicle time travelled and total delay on the road network also reduces by around 56%.