Reliability improvement in short headway transit services: Schedule-based and headway-based holding strategies

Improving service reliability is becoming a key focus for most public transport operators. One common operational strategy is holding. Holding vehicles can improve reliability, resulting in both shorter travel times and less crowding. In this paper, both schedule-based and headway-based holding strategies are analyzed in short headway services. Despite a significant focus on holding in current literature, some important aspects have not been researched previously. The main, new, variables are the maximum holding time, the reliability buffer time and, in the case of schedule-based holding, the percentile value used to design the schedule. Both a real line in The Hague (tram line 9) and hypothetical lines are analyzed with various levels of running time variability. Both headway-based and schedule-based holding have the largest effect if
deviations are high. When applying schedule-based holding and a maximum of 60 s. holding time is applied, the optimal value of the percentile value becomes about 65% for all lines analyzed. When no maximum holding time is applied, schedule-based holding is more effective, while there is no difference when the maximum holding time is set to 60s. This research also shows the effect of holding on crowding: An average level of irregularity of 20% could decrease to 15%, enabling either smaller capacity slack or less crowding.

Read the full paper: Paper TRR 2010 Van Oort

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