safetycritical

Safety-critical describes systems or components whose failure could result in loss of life, serious injury, or significant environmental or public harm. The term signals that safety considerations are central to the design, implementation, operation, and maintenance of the system. Safety-critical engineering requires explicit safety requirements, hazard analysis, and risk management integrated throughout the system life cycle.

Common domains include aviation (flight control and navigation), rail signaling and control, automotive safety systems (airbags, braking, stability control), medical devices (life-supporting equipment and implants), nuclear power plant instrumentation, and critical industrial automation. In these areas, designers use redundancy, fail-safe modes, monitoring, and fault tolerance to reduce risk and ensure safe operation even when components fail.

Practice in safety-critical engineering typically involves hazard analysis and risk assessment, development of a safety case, and rigorous verification and validation. It emphasizes safety-by-design, traceability of requirements, independent assessment, and robust configuration management. Software for safety-critical systems often undergoes heightened scrutiny, including formal methods, exhaustive testing, code reviews, and documentation of safety-related behavior.

Standards and frameworks provide structured approaches to achieve acceptable risk levels. IEC 61508 is a generic safety standard; sector-specific variants include ISO 26262 for road vehicles, EN 50126/50128/50129 for rail, DO-178C for avionics software, IEC 62304 for medical device software, and IEC 61511 for process industries. Safety integrity levels (SIL) or Automotive Safety Integrity Levels (ASIL) quantify the required reliability and fail-safety measures.

Maintaining safety-critical systems also involves ongoing monitoring, updates, and governance to address new hazards, software changes, and evolving threats, balancing safety, cost, and performance.