Perrow (1984)

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Perrow (1984): NAT (system level)

Perrow (1984) focuses at the system level of accidents in general, discussing two types in his Normal Accident Theory (NAT), which argues for the inevitability of disasters.

System Accidents (SA) are caused by complex interactions of multiple independent elements, and tight coupling of components, where if one fails there is no time to stop interconnected elements being seriously affected.

Component Failure Accidents (CFA) are defined by visible and foreseeable linear interactions between parts, and loose coupling in which the “domino” effect from any failed elements can be stopped.

Complex interactions and tight coupling are associated with SAs, which are most common in high technology systems, such as space travel. It is suggested that accidents are likely to occur in such systems, as it is very difficult to keep account of the multiple interacting parts.

Perrow does not extensively analyse the human element, although he does imply that the unpredictability of SAs and complex interactions is often caused by limited knowledge of relevant areas.

(For an analysis on Perrow's theory in relation to the NASA Challenger disaster, see essays)