afety critical components are components for which the occurrence of a single failure immediately creates a real risk of a major accident as defined in Article 3(12) of Directive (EU) 2016/798. A "serious accident" refers to a train collision or derailment in which at least one person is killed or at least five persons are seriously injured or which causes significant damage to rolling stock, infrastructure or the environment. It also refers to other accidents with similar effects which have obvious implications for railway safety regulation or safety management. Significant damage" is estimated by the investigating body as a direct cost of at least EUR 2 million.