Using repairable fault trees for the evaluation of design choices for critical repairable systems

Critical repairable systems are characterized by complex architecture and requirements. The evaluation of benefits produced by repair policies on the overall system availability is not straightforward, as policies can be very articulated and different. In order to support this evaluation process, the repairable fault tree (RFT) formalism revealed to be useful and suitable to represent complex repair policies by extending the existing fault tree formalism. In this paper we show how to exploit RFT advantages by evaluating the effects of different repair policies on the availability of the most critical component of ERTMS/ETCS (an European railway standard) systems: the radio block centre (RBC).