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Bus-based transitway or light rail? Continuing the saga on choice versus blind commitment

By David Hensher - posted Sunday, 15 October 2000

In most cities, buses move more public transport passengers than any other public mode. Buses, however, operate mainly on mixed-mode infrastructure, competing with cars and trucks, a regime that has not, in general, favoured bus services. This has provided a strong argument in support of rail systems on dedicated right-of-way, free from the movement constraints of competing modes. The rail emphasis, however, has often come at a great expense (with non-commensurate benefits), especially in corridors where the traffic levels are quite low, and door-to-door connection is a major influence on mode choice.

Bus-based transitways are often compared with light rail and frequently criticised in favour of light rail on the grounds of their lack of permanence because of the opportunity to convert the right-of-way into a facility for cars and trucks. However, several writers have put the case for bus-based transitways as a preferred option in most urban contexts where light rail has been evaluated. For many years, the arguments for and against light rail and bus-based transitway systems have persisted, with light rail often the victor on ideological grounds.

Unfortunately, light rail is increasingly the purveyor of substantial debt and operating subsidy. One very positive outcome of the ongoing light rail ‘debate’ is a recognition of the need to consider a larger set of public transport options than has traditionally been the case (including non-investment outcomes such as pricing and regulation) under a reasonable set of patronage assumptions.


This paper considers the evidence on the costs and benefits of light rail and bus-based transitway systems, with particular attention given to the biases in the positions taken by advocates of either form of public transport. The lessons to date reinforce the importance of delivering seamless transport services with good geographical coverage and sufficient flexibility to respond to changing market needs if we are to make a difference to the dominance of the automobile.

Taking a closer look at light rail and bus-based transitways

An increasing number of ‘new’ urban public transport systems are being developed in cities around the world, particularly light rail. The main objective of building such systems is to reduce car use, and so reduce road congestion and environmental damage. In many cases, the systems are expected to stimulate development.

When the evidence suggests that one can move three times as many people by dedicated bus-based transitway systems for the same cost, or the same number of people for one-third of the cost as light rail, one wonders about the rationality of urban planning. For example, a review of the proposal to extend the light rail system in Sydney between Central Railway and Circular Quay concludes that a re-designed bus system would provide a better immediate result at a greatly reduced cost. It asks:

‘... perhaps the investors themselves may have been taken for a ride by professional promoters... Or is it just an innocent mistake? The only thing clear is that there is something fishy about the whole affair.’

The New South Wales Government has recently announced a bus-based transitway in preference to LRT for the 20 km Liverpool–Parramatta Transitway (LPT). The LPT feasibility study compared light rail with a bus-based transitway and concluded that the bus system was significantly better in delivering higher levels of frequency (typically every three minutes compared to every nine minutes for LRT) with lower incidence of transfers compared to using a feeder bus to connect to light rail. Since transfers are a major source of dissatisfaction, this is a crucial issue in attracting patronage.

Although LRT costs per passenger kilometre are often argued to be lower than for bus systems, these comparisons are usually spurious because they are based on theoretical capacity and not on actual patronage. For LRT to provide an effective level of service it most likely has to operate at a frequency which does not maximise patronage on each trip. If this is the case, the advantage of light rail on operating costs per passenger kilometre is eroded. On construction costs, an integrated bus rapid transit system in Sydney can be expected to cost (in $M/km), based on the Brisbane Busways experience, from $0.1M/km with shared use of existing road, $1M/km with widening of an existing road and $1.5M/km in an exclusive corridor. In contrast LRT under the same three corridor contexts is respectively (on advice from GHD Transmark, March 1998) $3.4M/km, $2.10M/km and $2.02M/km.

Bus-based transitways function as efficient high-volume transport corridors where the operations are adapted from traditional bus practice and where substantial infrastructure investments are made in bus stops, terminals and vehicle types. Advantages of bus-based transitways over rail-based systems, such as the avoidance of transfers at terminals and the use of standard equipment, may correlate negatively with the capacity the bus-based transitway can achieve.

Comparing light rail costs with the average cost for buses is not very useful because it fails to compare the performance of equivalent types of service and fails to demonstrate the impact of implementing new rail services on total system financial performance. It is essential to compare rail performance to that of equivalent-density bus services and to include the productivity of new feeder bus routes whose costs are ‘caused’ by light rail, but which light rail management never includes with light rail costs in assessing the rail system’s financial performance. The evidence suggests that bus services that are typical of those replaced by rail services have much higher productivity than bus systems in general (benefiting from economies of density); in contrast, the new feeder bus services to support the rail network run at much higher costs and hence lower productivity than the bus system as a whole (derived from the Institute of Transport’s International Benchmarking subscription program for the bus and coach industry).

The evidence suggests that, in general, the impacts of light rail compared to bus-based systems are very limited in scale. The difference occurs because the evaluation framework that is often used as part of the development process usually ignores the latent (i.e. unsatisfied) demand for car use and so is liable to predict higher levels of patronage on the new system, and greater reductions in car use and consequential effects than will be the case. Furthermore, the forecast patronage on the new systems often do not justify the construction of light rail (except where estimates have been inflated), but the planning and legislative framework under which schemes are developed militates against innovation and more cost-effective systems. This suggests that there is a need to adopt funding formulae that relate levels of local and non-local expenditure to the overall benefits more carefully. There is substantial evidence from the literature that expenditure on new rail-based schemes diverts resources away from bus routes used by the lower-income population with no alternative mechanised mode of travel.

The message is simple and powerful: distance our thinking from an obsession with technology and move to study needs as a starting point of inquiry. Do not ask if light rail is feasible, but ask who the stakeholders are and proceed to investigate how they may best be served. Institutionally, the presence of economies of network integrity may force a review of the existing spatially bounded franchised arrangements for bus service provision in cities such as Sydney, London and Auckland. This is the challenge.

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This is an edited extract from a paper that first appeared in Road & Transport Research Vol 8 No 3, September 1999. The full paper can be viewed here.

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About the Author

Professor David Hensher is director of the Institute of Transport and Logistics Studies, in the Economics and Business Faculty, University of Sydney.

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