ABSTRACT

The topic dealt with in this chapter is optimizing the availability of a subset of the rail signaling system while keeping the life cycle cost (LCC) reasonable. Decision variables are related to design, maintenance, and operations. Maintenance policies include purely corrective, purely preventive (systematic), and mixed maintenance. The motivation has been onboard network applications in high-speed trains, but the results are of a wider applicability. Two types of network architecture (multifunction vehicle bus and Ethernet ring) are compared from a reliability, availability, and maintainability point of view, using the following steady-state performance measures:

Service reliability and service availability

Intrinsic reliability and asset availability

Continuous-time Markov chains (CTMCs) are used in order to estimate the impact of design, maintenance, and operations policies on those performance measures and LCC and, therefore, to guide the choices. Explicit results are given for availability as a function of failure rates, mean time to restore, failure detection probability and inspection frequency. Trade-offs are quantified. The limitations of CTMCs (e.g., they do not allow for the modeling of aging nor imperfect maintenance, unlike, for instance, stochastic Petri nets) do not introduce any bias in the results as one is interested here in comparing steady-state performance measures of two different systems.