Investigating bus priority parameters for isolated vehicle actuated junctions

Bus priority at traffic signals has been implemented in many cities around the world. At signalised junctions, priority can be given by altering signal timings in favour of approaching buses. In usual practice, this is achieved by either extending the green period for an approaching bus or recalling the green stage, if the signal is currently red for the bus. These bus priority methods reduce junction delays for buses and thus improve bus speed and reliability. At isolated junctions in the UK, the parameters used to implement these priority methods are only based on the requirements for green extensions. These parameters may not always be effective for recalls. This study was undertaken to explore whether bus priority benefits can be improved by considering new priority parameters effective for both methods. This research has involved the application of the VISSIM microscopic simulation software to evaluate existing and new strategies for bus priority at isolated signal controlled junctions operating under D-system vehicle actuation (VA). During evaluation, bus travel time savings and impacts on general traffic have been considered. The performance of these methods on various junction types has been evaluated. New advanced bus priority methods based on new priority parameters have been developed and their performance has been compared with the existing methods.