Application of functional safety on railways part II: Software development

As well as modelling & designing part, software development process is another major process in development of railway signalization systems. Early mechanical railway interlocking systems do not need such software development processes where all train traffic is controlled directly from signalboxes via mechanical tools and signalmen. Along with rising train speeds and densities the need of reliable and safe signalization systems including safe software increased. In this study, software development process of a signalization system for a railway yard including related CENELEC (European Committee for Electrotechnical Standardization) software standards is explained.