Dynamic Dispatch with Advanced Train Control System Data

Transit service reliability, measured by such performance measures as schedule deviation and headway distribution, is a priority for transit agencies. The successful implementation of strategies to keep transit fleets as close to schedule as possible aims to improve customer service and to operate a more efficient system. Common strategies to recover time lost in day-to-day operations include switchbacks, fallbacks, route changes, and reconfigurations. The San Francisco Municipal Transportation Agency, operator of intracity bus and light rail transit in San Francisco, California, uses all of these strategies to remedy unacceptably large headway deviances. Analysis was conducted to determine the potential effects on service reliability of an application of real-time route changes of light rail vehicles at the Embarcadero turnaround. Historical advanced train control system data are applied to a calculator that reassigns the trains on the basis of average headway lengths. The calculator simulates a scenario if such an automatic reassignment system is in place and reports the new schedule deviation and headway distribution. Weekday data for 1 month were applied to the calculator and analyzed to determine whether the reassignment methodology could save significant time in the average headways. The calculator was meant as the first step in the development of a more thorough operational algorithm that would reassign vehicles on the basis of multiple independent variables, to establish better on-time reliability and performance. In preliminary results, the automatic reassignment system showed time savings. Also discussed are current physical and operational constraints to implementation and next steps in model development.