Optimizing APM Failure-Mode Capacities

APM systems have consistently enjoyed high levels of reliability and availability, but they are not completely free from failures. Even with typical 99.5 percent availability, the pesky 0.5 percent amounts to more than 3 hours per month with passenger service impacts. When reduced service capacities are offered during periods of heavy demands, the results can be significant, in terms of passenger queuing, congestion, and time delays, even if the disruptions are relatively short in duration. This paper addresses the issues associated with conditions and opportunities that arise when failures occur in APM systems, but the focus of the paper is the development of system designs and operating strategies that enable the use of failure-mode routing of trains and other techniques to retain as much capacity over as much of the system as possible. The theories and techniques of failure-mode operation are given, along with case studies for several airport APM systems. A case is then made for a better industry response to the needs for higher failure-mode capacities, in terms of planning, procurement, design, implementation, and operations.