Esterel Technologies
What is EN 50128?
The railways industry currently relies on the EN 50128 Railway applications – Communications, signaling and processing systems – Software for railway control and protection systems
standard to provide a rational and consistent approach for the development of these safety-related systems. This international standard is part of a group of related standards, which also includes:
- EN 50126
Railway applications –The specification and demonstration of Reliability, Availability, Maintainability and Safety (RAMS)
- and EN 50129
Railway applications –Safety related electronic systems for signaling
.
This group of standards owes much of its direction and contents to the IEC 61508 standard that is a generic safety standard for electrical/electronic/programmable electronics safety-related systems. Both of these IEC and EN standards share the same philosophy in the sense that they:
- consider all relevant E/E/PES (Electrical/Electronic/Programmable Electronic Systems) and software safety life-cycle phases, from an initial concept phase to maintenance when these systems are used to perform safety functions;
- intend to introduce a
safety culture
; - have been conceived with a rapidly developing technology in mind;
- provide a method for the development of the safety requirements specification necessary to achieve the required functional safety for E/E/PE safety-related systems;
- use Safety Integrity Levels (SIL) for specifying the target level of safety integrity for the safety functions to be implemented by the E/E/PE safety-related systems;
- adopt a statistical risk-based approach for the determination of the SIL requirements;
- distinguish between safe and unsafe failure modes and require precautions for any possible undetected failures. The failure modes have a direct impact on the required Safety Integrity Level for a given E/E/PES.
The scope of an E/E/PES is presented in Figure 2.1 below:
In EN 50128, the Equipment Under Control (EUC) is subject to the certification project. The definition of the EUC depends on the scope of the certification. It can be:
- a complete interlocking system,
- a train speed control sub-system,
- any component of those system or subsystems.
