Which technology for urban public transport?

The merits of alternative urban and inter-urban public transport systems have been the subject of some debate, particularly since the publication of the UK's 1998 transport policy White Paper A New Deal for Transport. This current paper aims to assess some of the conflicting empirical evidence in the UK and abroad in order to allow an objective assessment of the policy implications. Section 2 presents an overview of technical and financial characteristics of mainly urban public transport systems, including capital and operating costs of recent light rail, guided bus, bus priority and suburban rail systems. Section 3 explores the evidence on the wider costs and benefits of systems in the UK, including wider environmental and socio-economic impacts. Although more expensive to build (under similar conditions), light rail systems often carry more passengers than ‘intermediate’ bus-based systems such as guided bus and segregated busways. There is not much between public transport systems on the basis of operating costs per passenger-km, except metro systems, which are twice as expensive to run as bus-based systems. When comparing revenues and operating costs directly, all modes except suburban regional rail appear capable of covering operating costs overall, with light rail and some of London's suburban rail services providing a marginal surplus of revenue. Average speeds of light rail and bus-based systems are comparable. In heavily congested corridors, new light rail systems can reduce journey times significantly, but such reductions are lower for bus-based systems, mainly because of the relatively limited amount of segregated right of way and priority at traffic signals. This highlights the fact that bus priority systems act primarily as ‘congestion busters’ at hot spots, which can be implemented more flexibly and gradually than for rail-based systems. Currently, electric propulsion appears to be the best option to mitigate air pollution and noise. However, new clean vehicle technologies will soon be in a position to play a major role in reducing emissions, in particular for bus-based systems. In terms of external costs per bus/train-km, environmental costs appear higher than accident costs, but lower than congestion externalities.