Functional safety and layer of protection analysis with regard to human factors

Traditionally, the human and organisational factors are incorporated into the probabilistic models through the failure events and their probabilities evaluated using relevant methods of human reliability analysis (HRA) (Gertman & Blackman 1994). In some HRA methods it is possible to introduce also the organisational factors, related in principle to the safety culture aspects. Correct evaluation of human behaviour and potential errors is a prerequisite of correct risk assessment and rational safety-related decision making in the safety management process (Swain & Guttmann 1983, Dougherty & Fragola 1988, COA 1998, Hollnagel 2005).