Development of safety criteria for railway software

Safety critical systems are those in which a failure can lead to serious and irreversible consequences. Nowadays digital technology has been rapidly applied to critical systems such as railways, aerospace, nuclear power plants, and vehicles. The main difference between an analog system and a digital system is that the software is the key component of the digital system. The digital system performs more varying and highly complex functions efficiently compared to the existing analog system because software can be flexibly designed and implemented. The flexible design makes it difficult to predict the software failures. This paper reviews safety standards and criteria for safety critical systems such as railway systems and introduces the framework for the software lifecycle. The licensing procedure for the railway software is also reviewed.