Normal Accidents

Normal Accidents

Normal Accidents: Living with High-Risk Technologies is a 1984 book by Charles Perrow, which provides an analysis of complex systems conducted from a social sciences standpoint. It was the first, or one of the first, to "propose a framework for characterizing complex technological systems such as air traffic, marine traffic, chemical plants, dams, and especially nuclear power plants according to their riskiness". Perrow says that multiple and unexpected failures are built into society's complex systems.

"Normal" accidents, or system accidents, are so-called by Perrow because such accidents are inevitable in extremely complex systems. Given the characteristic of the system involved, multiple failures which interact with each other will occur, despite efforts to avoid them. Such events appear trivial to begin with before cascading through the system in unpredictable ways to cause a large event with severe consequences.

Normal Accidents contributed key concepts to a set of intellectual developments in the 1980s that revolutionized the conception of safety and risk. It made the case for examining technological failures as the product of highly interacting systems, and highlighted organizational and management factors as the main causes of failures. Technological disasters could no longer be ascribed to isolated equipment malfunction, operator error or acts of God.

The inspiration for Perrow's books was the 1979 Three Mile Island accident, where a nuclear accident resulted from an unanticipated interaction of multiple failures in a complex system. The event was an example of a normal accident because it was "unexpected, incomprehensible, uncontrollable and unavoidable".

Perrow concluded that the failure at Three Mile Island was a consequence of the system's immense complexity. Such modern high-risk systems, he realized, were prone to failures however well they were managed. It was inevitable that they would eventually suffer what he termed a 'normal accident'. Therefore, he suggested, we might do better to contemplate a radical redesign, or if that was not possible, to abandon such technology entirely.

In Normal Accidents, beside the nuclear power industry, Perrow examines the chemical industry; aircraft and air traffic control; marine transportation; dams and mines; and the space program.

A German translation of the book was published in 1987 with a second edition in 1992.