Operational Schedule Flexibility, Train Velocity and the Performance Reliability of Single-Track Railways


Freight shippers and travelers demand a consistent level of service from transportation systems, including railways. Inventory and train connections are more efficiently managed when the total time for railways to move freight or passengers between origin and destination is predictable. One approach to achieve consistency is structured operations where trains are dispatched according to predetermined schedules. By precisely planning the meet and pass interactions to match available track infrastructure, train delay is minimized, train velocity is increased and total runtimes are highly predictable. In North America, the economics of transporting many freight commodities requires a certain amount of schedule flexibility that results in sub-optimal train conflicts and introduces additional train delay. Theoretically, the same total running time and train velocity can be achieved under these flexible operations by increasing the maximum allowable train speed on the line to compensate for the delays. To investigate the equivalency of structured operations at lower speeds versus flexible operations at higher speeds, a representative single-track route was simulated with Rail Traffic Controller. From a baseline minimum-delay schedule, the experiment design increased both maximum allowable speed and schedule flexibility to examine the interaction between these factors and the distribution of runtime and train velocity response for various traffic volumes. Simulation results suggest a slight shift from structured to flexible operations requires a substantial increase in operating speed to maintain runtime and velocity. Decreasing schedule flexibility to facilitate reduced maximum operating speed (and fuel and motive power savings) shows little return until operations become completely structured.