Abstract
Critical state of operation is reached by a system when it is exposed to an unexpected coincidence of faults (such as periodic rapid increase of the service demand, unavailability of a significant proportion of vehicle operators, simultaneous breakdown of all or a large part of the vehicle fleet). This leads to complete disruption of the transportation system, which persists even after the faults are removed. The duration of critical state of operation is defined as the time needed to resume normal operation after such an incident. It is shown that this time can be predicted using the simulation tools. Furthermore, a contingency plan is proposed, based on relocation of some resources between independent parts of a hierarchically organized transportation system. This contingency plan is analysed to determine the optimal percentage of resources to be relocated and the duration of this relocation.