Light rail and bus priority systems: Choice or blind commitment?

Abstract

The debate over light rail transit (LRT) systems is often a confrontation between advocates and opponents of LRT systems. It is difficult to separate real evidence from opinion about LRT. This paper reviews evidence and viewpoints about LRT systems in comparison to bus priority systems (BPS), the latter often combined with high occupancy vehicle (HOV) lanes. Bus-rail comparisons are difficult because people tend to think of existing bus services which are constrained to share congested roads with cars for most of their routes. Extensive dedicated busways or HOV lanes are more akin to LRT systems, and there are few examples of these bus priority operations. BPSs are capable of moving comparable volumes of people at less cost than LRT. Where BPS and HOV systems are in use, they appear to move more people than are being moved in established LRT systems. LRT systems may have an advantage in influencing land-use in a way which will promote greater reliance on public transit, but it appears that similar impacts can be achieved by bus-based systems. There is a need for closer study and analysis of busways and HOV lanes. It is also important to recognize that neither BPS nor LRT are likely to have much impact on overall mode split unless substantial steps are taken to discourage single occupant motor vehicles.