scope:

This European Standard specifies procedures and technical requirements for the development of programmable electronic systems for use in railway control and protection applications. It is aimed at use in any such area where there are not safety implications. These may range from the very critical, such as safety signalling to the non-critical, such as management information systems. These systems may be implemented using dedicated microprocessors, programmable logic controllers, multiprocessor distributed systems, larger scale central processor systems or other architectures. It is applicable exclusively to software and the interaction between software and the system of which it is part. Software safety integrity levels above zero are for use in systems in which the consequences of failure could include loss of life. Economic or environmental considerations, however, may also justify the use of higher software safety integrity levels. It applies to all software used in development and implementation of railway control and protection systems including application programming, operating systems, support tools and firmware. Application programming comprises high level programming, low level programming and special purpose programming (e.g. Programmable Logic Controller ladder logic). It is not intended to be retrospective. It, therefore, applies primarily to new developments and only applies in its entirety to existing systems if these are subjected to major modifications. For minor changes, only clause 16 applies.