Abstract
This article introduces a research aiming at the development of a decision support system concerning the approval of automated railway transportation systems. The objective is to evaluate the degree of compliance of the transportation system according to the security standards by the simulation of the scenarios of accident. To reach this target, the authors envisaged an approach Rex (Return of experience) who draws lessons of accidents lived and/or imagined by the experts of the analysis of security in the NRITS (National Research Institute on Transports and their Security): currently IFSTAAR. The approach consists in offering aid to the experts by a reuse of the accidents already validated. This approach provides to the experts a class of similar accidents situations to the new case. The case-based reasoning is then exploited allowing choosing one under group of historical cases that can help in the resolution of the new case introduced by the experts.