A new strategy for differential bus priority at traffic signals for high frequency services

The need for sustainable transport operations in cities is focusing more attention on the needs of buses to provide fast, frequent and reliable services. One favoured measure is bus priority at traffic signals, particularly where roadspace is limited. With increasing use of Automatic Vehicle Location (AVL) systems, it is now possible to provide ‘differential’ priority, where different levels of priority can be awarded to buses at traffic signals according to chosen criteria. At present, common strategies are based on the comparison of the time headway of a bus with the scheduled headway. However, this paper shows that greater regularity benefits could be achieved through a strategy where priority for a bus is based not only on its own headway, but also the headway of the bus behind. This paper discusses this new strategy,demonstrates its benefits on a theoretical basis and provides initial simulation results.