Safety-Critical Interlocking Software Development Process for Fixed-Block Signalization Systems

Reliability is defined as “ability of an item to perform a required function under given conditions for a given period of time” in CENELEC (European Committee for Electrotechnical Standardization) EN 50128 document where software development requirements for railway applications are defined. Similarly, Software Reliability is defined as the probability of failure-free software operation for a specified period of time in a specified environment which is also important factor affecting system reliability (Pan, 2012). Systems such as railway signalization systems, where small errors can result in fatal accidents and death of several people or possibility of unwanted risks (like component malfunction) is high, also need software with high reliability. In this study, some parts of the safety-critical interlocking software development process for the Turkish National Railway Signalization Project (TNRSP) executed in cooperation with Istanbul Technical University (ITU) and The Scientific and Technological Research Council of Turkey (TUBITAK) for Turkish State Railways is defined.