Modelling the net traffic congestion impact of street car networks – A Melbourne, Australia case study

Streetcars (trams) operating with other public transport modes such as train and bus has contributed to reduce urban traffic congestion in many cities around the world, particularly in inner cities. However, there has been no attempt to examine the net network-wide impacts of streetcar networks on vehicular traffic and congestion. This paper presents a new method for assessing the net traffic congestion effects associated with tram operations in Melbourne, Australia. These impacts are determined by comparing congestion measures in two scenarios: “with tram” and “without tram”. To investigate the positive impact of trams, it is assumed that there is a mode shift to car from trams when tram operations are removed. The congestion level increase caused by this mode shift is interpreted as the positive effect of trams. In contrast, the negative impacts of trams are explored by considering the curbside tram stop impact and the effect of reallocation of priority tram lanes on traffic flow. Findings show that the tram network in inner Melbourne results in a net 3.4% decrease in vehicle time travelled and total delay on the road network in these areas. It also contributes to reduce the number of moderately congested links by 16%. However, the impact of trams in the middle metropolitan areas is not significant due to the low density of tram routes in these areas. Areas for future research are suggested such as exploring the spatial distribution of the share of mode shift to car and the long-term effect of trams on traffic.