Traffic congestion relief associated with public transport: state-of-the-art

Public transport (PT) influences the urban road system in many ways, including traffic congestion, environment, society, safety and land use impacts. While there are many studies focusing on the benefits of PT, research on congestion impacts, a fundamental component of any analysis of transport performance, associated with PT has received little attention. This paper aims to review the traffic congestion impacts of PT and how they are assessed. Traffic congestion is most commonly related to vehicle travel; yet, the real measure of congestion in transport systems is people travel. This paper looks at the appropriateness of existing traffic congestion measures and how suitable they are for measuring the impact of an existing PT system in the short-term. The literature review indicates that most studies relating to the congestion impacts of PT have used vehicle-based congestion measures. People-based measures may be more appropriate in assessing PT impacts. The paper also proposes a new framework for looking at the short-term effects of an existing PT system on traffic congestion. It suggests a few areas where further work can be undertaken to improve our understanding of traffic congestion incorporating PT such as exploring the mode shift from PT to car, estimating network-wide PT congestion creation impacts and determining the net congestion impact of PT.