Differential Priority for London's Buses at Traffic Signals Using iBus

Transport for London (TfL, United Kingdom) has recently procured a Global Positioning System (GPS)-based Automatic Vehicle Location (AVL) system, iBUS. This system has facilities to monitor all the buses in a network. This paper describes how differential priority works in iBUS and explores various implementation issues including system testing and priority strategy to enhance bus priority at traffic signals in London. The authors note that knowledge of the location of all the buses in a network, available at the control center, could be utilized to provide more efficient priority to buses at traffic signals. Differential priority gives different levels of priority to buses at traffic signals to improve their punctuality or regularity. Benefits from differential priority include: improved service regularity, which reduces passenger waiting times; targeting buses with a higher occupancy, because late buses typically have to pick up more passengers; the possible provision of a higher level of priority and less disruption to general traffic, because fewer buses are awarded priority; and less conflicting priority for buses where there is large bus flow in conflicting traffic signal stages. Research on the implementation issues of differential priority is currently being carried by the Transportation Research Group (TRG) at the University of Southampton for TfL. The authors conclude that preliminary technical test results show that there is a real opportunity to provide effective differential priority using iBUS to build more efficient and beneficial bus priority at traffic signals in London.