Simulation of rare events in transportation systems

Prior to the deployment of any new or replacement component within a transportation system, it should be demonstrated that the modified system meets or exceeds the safety requirements of the original system. Since the occurrence of a mishap in such a system is a rare event, it is neither cost nor time effective to build and to test a prototype in an actual system prior to deployment. The Axiomatic Safety-Critical Assessment Process (ASCAP) is a simulation methodology that models the complete system and analyzes the effects of equipment changes. By carefully constraining the amount of the overall system state space required for analyses, it probabilistically determines the sequence of events that lead to mishaps. ASCAP is applicable to any transportation system that is governed by a well-defined operational environment.