Terminology

Light rail is a modern form of public transport that runs on rails. It shares many characteristics with heavy rail system such as metros and suburban rail, but has lower capacity. Its main advantage over these other systems is that it is cheaper and more flexible since it can be operated on the road in mixed traffic. Generally this is not advisable since it will suffer from the effects of congestion, but it can also be run at the margin or along the median of highways. Usually it has a much simpler signalling than heavier rail systems, often relying on the driver's judgement rather like a bus, particularly in mixed traffic conditions. When it is running along a highway it can be given priority at signalised junctions. Light rail can also be elevated or built in tunnel. Often a combination of these is used to match local circumstances, for example by using disused railway embankments to provide a fast interurban route with street running in town centres.

Light rail is nearly always powered by electricity which is usually supplied through overhead wires, but can be supplied through a third rail system. The latter can only be used when the system is completely segregated from the public except at stations. It is also possible to have driverless automatic systems which also have to be segregated.

Light rail has much in common with the tram. In some ways it is simply a modern version of the tram, but in some cities, such as Amsterdam and Melbourne where there are extensive tram systems, light rail lines are being built, often with some segregation, to provide high speed links to areas not previously served by trams. Generally, light rail is modern, has at least some segregation from other traffic, and is powered by electricity. New systems are usually the subject of extensive marketing campaigns, and branded with a suitable name such as 'Metrolink' or 'Supertram'.

The growth of light rail

Light rail grew in popularity during the 90s in the UK with the new Labour government declaring that there would be 25 light rail transit systems built in the UK (this prediction is now looking decidedly uncertain). Since 1970, 61 metros and 78 light rail systems have opened as Babalik (2000) has shown, using data from Taplin (1997, 2000). Given the complexity of definition it is difficult to be clear which was the first modern light rail system. Rogers (1975) recognises the system in Edmonton in Canada which opened in 1976 as the first, regarding all previous examples as extensions to, or rehabilitation of, existing tram systems. The table below shows the distribution of new light rail systems around the World. It also shows the number of new metros for comparison.

Source: Babalik (2000) based on Taplin (1997, 2000).

It can be seen that in the 1970s the number of metros built outnumbered the number of light rail systems. Since then the picture has reversed completely, with 69 new light rail systems opened since 1980 compared with 38 new metros. North America led this trend in the 1980s, but since then most activity has been elsewhere. Now there are more light rail systems than metros in Western Europe and North America (Babalik, 2000).

Since 2005 in the UK concern from the Treasury at spiralling costs of light rail has led to a mothballing of several planned projects. At the time of writing (July 2006) the plans for light rail on Merseyside, South Hants, Bristol and others are looking at best uncertain. There does appear to have been a movement by the UK government towards favouring bus-based solutions - possibly also influenced by the apparent success of Transport for London in increasing bus patronage.

Why introduce light rail?

A study of the decision process underlying the choice of technology (metro, light rail, guided bus or conventional bus) for a number of systems around the World was carried out at the Centre for Transport Studies at University College London in 1991-1994 under the UTOPIA project. As part of that work interviews were held with a number of experts involved in the development of some systems to collect information on various aspects of the decision-making process including discussion on why the systems were developed. A postal survey was carried out on other systems. The status of systems examined for their objectives are shown, as are the objectives for developing the systems cited by the experts.

Source: Mackett and Edwards (1998).
Note: The surveys upon which these data were based were carried out in 1992-1994. The status information has been updated.

The table below "objectives of developing light rail systems" indicate that the most popular reason for developing the systems was to stimulate development. In three cases, Brisbane, Copenhagen and London Docklands, the light rail system was an integral part of the redevelopment of a large area. It is not clear what the mechanism is that underlies this process although for the Calgary, Croydon, Leeds and Dallas systems, the objective was to help stimulate development in the city centre by providing easier access to the economic activities there. Some experts suggested that the mechanisms are related to 'image', 'confidence' and so on. The only evidence cited was in the case of Leeds (Pope, 1994) where a survey of businessmen showed that many of them would support the investment in a new public transport system. Apparently some of the major store chains would be more likely to expand their shops in Leeds if such a system were developed.

The second most common objective cited was 'to improve public transport'. It might be argued that this is axiomatic, but usually it was linked to a social objective, for example, providing better access for those without a car. A related issue is that of serving the city centre, because segregated public transport is very good at this, as it can serve efficiently the main corridors which focus on the city centre where most economic activity takes place and interchange is easier. An interesting variant on this is to provide transport from the inner city where there is often high unemployment outwards to newer employment centres. This was mentioned for the Croydon, Tyne and Wear and West Midlands systems.

'To reduce traffic congestion' was cited in 10 cases, implying that a significant transfer of trips from car to the new system was anticipated. In five cases, 'To improve the environment' was cited. Generally this means reducing atmospheric emissions from cars and so is related to reducing car use. These two reasons imply that some planners believe that developing new light rail schemes can reduce car use significantly.

The 'other' reasons include a variety of factors. For example, the Manchester and Tyne and Wear systems were developed as ways of dealing with heavy rail lines in need of renewal. Replacing heavy rail by light rail meant that the system could be brought into the city centre to improve access there. In Dallas, a prime motivating factor was to help to promote Dallas as a 'World city'. The logic was that all 'World cities' have a modern public transport system so Dallas had to have one.

Source: Mackett and Edwards (1998).
Note: The information in this table is based upon interviews and postal surveys of experts involved in the development of the systems. For the list of experts see Mackett and Edwards (1998). The surveys upon which these data were based were carried out in 1995-1996.