Safety Requirements

Safety requirements and their role in determining the acceptability of a safety-critical system.

Many safety standards use the concept of a safety requirement to ensure that the system carries out the functions needed to make it acceptably safe. For the safety requirements to achieve this (in terms of the risk reduction being both sufficient and necessary), an adequate risk assessment must have been carried out.

Safety requirements may relate to the frequency of various failure modes of components of a system, any of the other possible layers of protection intended to prevent a failure from turning into an accident, or processes involved in the development of a system.


Without adequate identification and derivation of safety requirements, the system may not be preventing the right or any hazards, and you may build a high integrity system which is reliably unsafe.


Safety requirements also often lead to the determination of Safety Integrity Levels (SIL) as one way of expressing the relative importance of meeting each safety requirement.