2SMRT Buses Ltd, SINGAPORE
A phenomenon known as equal headway instability predicts that in the absence of explicit control, buses naturally bunch together. This adversely affects the consistency of waiting times for commuters which generally results in customer dissatisfaction. In 2014, the Land Transport Authority of Singapore (LTA) adapted from London a performance metric known as excess waiting time (EWT) that aims to monitor the regularity of arrival time of buses in selected stations. In this work, we report the performance results of selected bus services that have been monitored in the second half of 2014 calculated using historical automated vehicle location data. Based on these results, we show that fluctuations in commuting demand significantly impact the measured EWT. By collating the results of bus headway for different services, we also verify that given an adequate sample size, the difference between actual headway and scheduled headway for different services can generally be closely approximated by a normal distribution. Finally, we provide recommendations on the usefulness of EWT and how it can be improved in the context of Singapore’s public bus system, which is primarily composed of high frequency bus service that experiences large fluctuations in commuter demand.