The risk is reduced to a tolerable level by applying safety functions which may consist of E/E/PES, associated mechanical devices, or other technologies.
IEC 61508 has the following views on risks: Specific techniques ensure that mistakes and errors are avoided across the entire life-cycle.
Errors introduced anywhere from the initial concept, risk analysis, specification, design, installation, maintenance and through to disposal could undermine even the most reliable protection.
The standard advises that 'Either qualitative or quantitative hazard and risk analysis techniques may be used' and offers guidance on a number of approaches.
One of these, for the qualitative analysis of hazards, is a framework based on 6 categories of likelihood of occurrence and 4 of consequence.
The requirements include appropriate quality control, management processes, validation and verification techniques, failure analysis etc.
[3] The MISRA project was conceived to develop guidelines for the creation of embedded software in road vehicle electronic systems.
[4] This document provided the first automotive industry interpretation of the principles of the, then emerging, IEC 61508 standard.
[5] MISRA C has gone on to become the de facto standard for embedded C programming in the majority of safety-related industries, and is also used to improve software quality even where safety is not the main consideration.
It is intended to cover the development of software for railway control and protection including communications, signaling and processing systems.
IEC 61511 is a technical standard which sets out practices in the engineering of systems that ensure the safety of an industrial process through the use of instrumentation.
IEC 61513 provides requirements and recommendations for the instrumentation and control for systems important to safety of nuclear power plants.
An overview list of safety norms specific for nuclear power plants is published by ISO.