Normal accidents are failures that are considered inevitable, or at least highly likely, given the inherent complexity and tight coupling of human and technological systems, particularly in high-risk industries such as nuclear power, aviation, and chemical processing. This theory, developed by sociologist Charles Perrow, suggests that in such complex systems, multiple unexpected failures can interact in unforeseen ways, leading to accidents that are not simply the result of isolated errors but are a systemic outcome of the organisation and technology involved. The interactive complexity and tight coupling of these systems make it difficult to predict or prevent all potential failure combinations, leading to what Perrow terms "normal" accidents, meaning they are a normal, albeit infrequent, feature of such systems.