Excess Time, a Measure of System Repairability

The performance of systems subject to failure and repair cycles can be described by a variety of stochastic processes. Downtime is a measure of system worth which is commonly found in the reliability literature. Another measure, excess time, has been proposed in a recent paper. Both downtime and excess time are measures of the accumulated time during which the system has been inoperative. The parameter t of excess time counts only productive units of time. Thus B(t) is the excess of unproductive time over productive time. The properties and applications of excess time are reviewed and summarized.