Perrow’s Normal Accidents

Charles Perrow Normal Accidents: Living with High-Risk Technologies Basic Books, 1984

A classic.

It was 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 argues that multiple and unexpected failures are built into society’s complex and tightly coupled systems. Such accidents are unavoidable and cannot be designed around.

Perrow said that, while operator error is a very common problem, many failures [of technological systems] relate to organizations rather than technology, and big accidents almost always have very small beginnings. Such events appear trivial to begin with before unpredictably cascading through the system to create a large event with severe consequences

Perrow identifies three conditions that make a system likely to be susceptible to Normal Accidents. These are:

  • The system is complex
  • The system is tightly coupled
  • The system has catastrophic potential

The strong recommendation is not to develop, or at least not to rely on, technological systems with the above properties.

See Also

Gerstein and the Ellsbergs take a broader view of a broader range of systems.

The University of Essex considers UK government blunders, including attempts to develop technological systems.

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