Railway interlocking process - Building a base for formal methods

Railway interlocking is designed to prevent trains from colliding. Generally speaking current systems are safe due to the processes that signalling systems have to follow as well as implementation procedures that interlockings are compliant with. Even the processes and procedures are very advanced; there are still train crashes that are triggered by interlocking faults. However, the interlocking faults are mainly related to poor maintenance of the systems or/and changes to the original designs without correct authorisation. While those areas are worth exploring to search some improvements it is also important that interlocking will progress its development toward intelligent transport system reinforcing maintenance functions.