An Approach to Predicting Passenger Operation Performance from Commuter System Performance

In passenger operation, one often is concerned with on-time performance. On-time performance in commuter operation is measured by the difference between the actual arrival or departure time and scheduled arrival or departure time, respectively. A common practice is to use a time threshold value, and measure the schedule deviation. If the schedule deviation is greater than the set threshold value, the operational performance is considered to have failed. Otherwise, the operational performance is considered successful. At the time a commuter system is commissioned, the system delivers its predicted performance based on its component and subsystem performance, usually expressed in Reliability, Availability, and Maintainability (RAM) measures. The Reliability is usually expressed in Mean Time Between Failures (MTBF) for ground based equipment, and Mean Distance Between Failures (MDBF) for onboard equipment. System failures, however, do not necessarily cause schedule deviation, and if they do, they do not necessarily cause a schedule deviation above the preset threshold value. This paper presents a method that can be used to predict passenger operation performance measured in schedule deviation with a preset threshold value, from delivered commuter system performance expressed in MTBF or MDBF. When used in procurement, this method lends commuter railroads a means to specify system performance in accordance with the target passenger operation performance. For systems already in service, this method allows a commuter railroad to make selective improvements that bring the highest return on investment.