HEP meaning

HEP (Human Error Probability) describes, in legal practice concerned with health and safety law, a quantified estimate of the chance that a person (typically an operator) will perform a defined task incorrectly or fail to perform it. It is used in risk assessments, safety cases and ALARP/SFAIRP analyses to evidence whether risks have been reduced so far as is (reasonably) practicable, and in expert evidence on foreseeability, causation and the adequacy of controls. HEP is not defined in legislation or case law; it is a descriptive engineering measure derived from human reliability analysis. It assigns a probability to a specific action in a stated context, taking account of factors such as time pressure, complexity, training and procedures. It is commonly applied in high-hazard sectors (e.g. nuclear, chemical, offshore, rail, aviation and healthcare) when demonstrating legal compliance with health and safety duties. Across England & Wales, Scotland, Northern Ireland and Ireland, usage is broadly consistent, though regulatory frameworks differ. In all jurisdictions, HEP can inform decisions on reasonably practicable risk reduction, underpin safety reports and regulatory submissions, and support or challenge claims and enforcement by showing whether a human error was foreseeable and what barriers or safeguards were justified.