* Corresponding Author Email Address: [email protected] International Journal of Railway Research The Safety Level of Railway Infrastructure and Its Correlation with the Cost of Preventive and Mitigation Measures A-M. Ioannidou 1 , C. Pyrgidis 2,* 1 Hellenic Institute of Transport (HIT)-CERTH, Greece 2 Aristotle University of Thessaloniki, Greece A B S T R A C T This paper develops a methodology which allows the correlation between the cost which is required for the application of preventive and mitigation measures dealing with accidents which occur within a railway system and the improvement of the level of safety as a result from their implementation. The safety level is expressed either quantitatively, by the decrease of “fatality risk” indicator or other indicators as defined by the European Railway Agency (ERA), or qualitatively by the change of “risk level”, as defined by CENE LEC. Research focuses on accidents and, more specifically, on accidents caused by the railway infrastructure. The proposed methodology may be applied in all incident categories and for various causes subject to appropriate modifications . This research pape r is a first attempt to provide answers in an important research field for railway companies, as many issues should be further explored.More specifically, further research shall include a) with respect to the approach based on the change in the “ risk level ” : definition of the values of each frequency and severity category, for each incident and cause category b)w ith respect to the approach based on the indicators: selection of an appropriate indicator for each incident category (definition of indicator, mea surement units).