The End of the Bus Lane.
BALCOMBE R J, DAUGFIE, RTY G and YORK I, Transport Research Laboratory, UK.
The use of bus lanes to give priority to buses in congested traffic is well established. However by themselves they do not provide a universal solution to the problems of making bus services faster and more reliable: there are many congested bus routes wh
The use of bus lanes to give priority to buses in congested traffic is well established. However by themselves they do not provide a universal solution to the problems of making bus services faster and more reliable: there are many congested bus routes where there is insufficient road space to install bus lanes, and bus lanes have to be interrupted at junctions to allow movement of traffic on other routes.
There has been considerable interest in recent years in new techniques, used in conjunction with, or instead of, bus lanes for giving priority to buses. This project was commissioned by the Department of Transport to monitor and evaluate examples of innovatory methods designed to facilitate the passage of buses through junctions where bus lanes are interrupted.
The project evaluated six case studies: two bus advance areas at signal-controlled junctions (London), and one at a roundabout (Doncaster); a bus gate approached by buses using a less heavily used lane than that used by non-priority traffic (Aberdeen); a priority lane shared by buses and goods vehicles, bypassing a signal controlled junction (Newcastle upon Tyne); and an extension of a bus lane to a junction stop line, with shared use by buses and left-turning traffic (Birmingham). A model was also developed to investigate the likely effects of modifying bus lane set-backs on approaches to roundabouts to allow the optimal set-back distances to be determined.
A with-flow bus lane is normally set back from the junction stop line, but buses could be given more priority (while still retaining fitll junction capacity) by stopping non-priority traffic at a secondary stop line at the end of the bus lane. This creates a bus advance area, the simplest form of which is illustrated in figure 1. The 'pre-signal' controls non- priority traffic and is RED for most of the main signal RED stage, but buses are free to proceed to the main junction stop line in an area which is otherwise dear during the RED stage. Shortly before the main signal turns GREEN, non-priority traffic is released by the pre-signal in time to ensure the saturation flow at the junction is maintained. The length of the pre-signal RED is therefore critical to the success of the scheme.
In principle, this arrangement should have little or no effect on non-priority traffic, which queues at the secondary rather than the main stop line. Buses arriving during the green stage should also be unaffected, but those arriving during the pre-signal red stage avoid any queue and thereby save some time. Furthermore, those needing to use right- hand lanes can get into them without obstruction by non-priority traffic.
Association for European Transport