A strategic approach to railway signalling software

Recent developments in microelectronic technology have revealed that they offer a technically superior performance to railway signalling at a lower cost, and microelectronics is now being applied to almost every vital signalling function. In order to achieve a high level of reliability and safety in the software it is essential that tight managerial controls are adopted throughout all stages of development, manufacture, operation and maintenance. Safety requirements, specifications, system design and software design should be well defined and documented. These approaches to software for railway signalling are all compiled in a set of guidelines. They have been built on the long experience in the relay-based signalling and deliberate investigation on the application of microelectronics to signalling, and they are being improved through new experience in the microelectronic signalling age. The authors describe these activities in developing and evaluating the software for railway signalling in Japan