Impacts of holding control strategies on transit performance: a bus simulation model analysis

Transit operators are interested in strategies to improve service reliability as it is an important measure of performance and level of service. One of the common practices aimed to reduce service unreliability is holding control strategies. The design of these strategies involves the selection of a set of time point stops and the holding criteria for regulating the departure time. In order to analyze the impacts of holding strategies on transit performance, it is necessary to model dynamically the interactions between passenger activity, transit operations and traffic dynamics. An evaluation of different holding criteria and number and location of time point stops was conducted using BusMezzo, a dynamic transit simulation model. The holding strategies were implemented in the model and applied to a high frequency trunk bus line in Stockholm. The analysis of the results considers the implications of holding strategies from both passengers and operator perspectives. The analysis suggests substantial gains from implementing holding strategy based on the mean headway from the preceding bus and the succeeding bus. This strategy is the most efficient in terms of passenger time savings as well as fleet costs and crew management.