Evaluation of bus bridging scenarios for railway service disruption management: a users’ delay modelling tool

Unexpected transit service disruptions degrade the quality of service provided to the public. Bus bridging is considered a key response strategy used to handle metro service interruptions, where buses are retracted from scheduled services and deployed to offer shuttle services along disrupted segments. Most transit agencies rely on ad-hoc approaches (based on experience) to determine which buses should be dispatched from the scheduled services, with little (or no) consideration of the impacts on users’ delays. This paper presents a practical tool to estimate the total users’ delay associated with a user-specified bus bridging plan. The tool is based on deterministic queueing theory. The total delay is composed of two components; direct delays of affected metro passengers along the disrupted segment and indirect delays of bus riders on the routes from which shuttle buses are dispatched. The tool utilizes several input data, including travel times, train load information, boarding and alighting passenger counts, bus frequencies, and routes’ cycle times. It provides transit practitioners and operational managers with a valuable instrument for evaluating different bus bridging scenarios. A case study of the transit network in Toronto is used to illustrate the tool’s functionality.