Bunching and Headway Adherence Approach to Public Transport with GPS

Emerging GPS devices enable new data collection opportunities for transit performance monitoring. In addition to the fact that GPS devices can replace labor-intensive survey techniques, they also collect traffic information throughout transit routes that the traditional fixed loop detectors cannot. If public transit vehicles are equipped with GPS devices, it is possible to monitor the performance of public transit services throughout the routes and alert the associated authorities at significantly lower costs about potential problems for corrective actions to be taken. Transantiago, a major public transit service provider in Santiago, Chile, has recently installed GPS sensors on all its vehicles which provides an excellent venue on which an innovative transit monitoring methodology can be modeled and applied. This paper first conducts current-status analysis on distributions of headways throughout a route in Santiago by processing extensive raw GPS data from transit vehicles. Then, unique transit headway adherence indices are developed with respect to the expected passenger waiting time and are presented in forms of two-dimensional tempo-spatial graphs. The analysis of real-life data collected from bus GPS probes in Santiago, Chile indicates that GPS devices in transit buses can effectively provide the proposed performance measures throughout the route on a daily basis.