Modeling Accident Causation as Event Chains

Assumption 2 Accidents are caused by chains of directly related events. We can understand accidents and assess risk by looking at the chain of events leading to the loss. 

Some of the most important assumptions in safety lie in our models of how the world works. Models are important because they provide a means for understanding phenomena like accidents or potentially hazardous system behavior and for recording that understanding in a way that can be communicated to others. 

An underlying assumption of all accident models is that there are common patterns in accidents and that they are not simply random events. Accident models impose patterns on accidents and influence the factors considered in any safety analysis. Because the accident model influences what cause(s) is ascribed to an accident, the countermeasures taken to prevent future accidents, and the evaluation of the risk in operating a system, the power and features of the accident model used will greatly affect our ability to identify and control hazards and thus prevent accidents. 

The earliest formal accident models came from industrial safety (sometimes called occupational safety) and reflect the factors inherent in protecting workers from injury or illness. Later, these same models or variants of them were applied to the engineering and operation of complex technical and social systems. At the beginning, the focus in industrial accident prevention was on unsafe conditions, such as open blades and unprotected belts. While this emphasis on preventing unsafe conditions was very successful in reducing workplace injuries, the decrease naturally started to slow down as the most obvious hazards were eliminated. The emphasis 

Basic causes (personal and job factors) that lead to 

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