![]() ![]() The system produces failures when a hole in each slice momentarily aligns, permitting (in Reason's words) "a trajectory of accident opportunity", so that a hazard passes through holes in all of the slices, leading to a failure. The holes in the slices represent weaknesses in individual parts of the system and are continually varying in size and position across the slices. ![]() In the Swiss cheese model, an organization's defenses against failure are modeled as a series of imperfect barriers, represented as slices of cheese, specifically Swiss cheese with holes known as " eyes", such as Emmental cheese. Each slice will have holes of varying sizes and positions. Holes and slices Emmental cheese with eyes. ![]() It is sometimes called the "cumulative act effect".Īlthough the Swiss cheese model is respected and considered a useful method of relating concepts, it has been subject to criticism that it is used too broadly, and without enough other models or support. Reason of the University of Manchester, and has since gained widespread acceptance. The model was originally formally propounded by James T. other slices of cheese), to prevent a single point of failure. a hole in each slice in the stack aligning with holes in all other slices), since other defenses also exist (e.g. Therefore, in theory, lapses and weaknesses in one defense do not allow a risk to materialize (e.g. It likens human systems to multiple slices of Swiss cheese, which has randomly placed and sized holes in each slice, stacked side by side, in which the risk of a threat becoming a reality is mitigated by the differing layers and types of defenses which are "layered" behind each other. The Swiss cheese model of accident causation is a model used in risk analysis and risk management, including aviation safety, engineering, healthcare, emergency service organizations, and as the principle behind layered security, as used in computer security and defense in depth. In this diagram, three hazard vectors are stopped by the defences, but one passes through where the "holes" are lined up. Model used in risk analysis The Swiss cheese model of accident causation illustrates that, although many layers of defense lie between hazards and accidents, there are flaws in each layer that, if aligned, can allow the accident to occur. ![]()
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