Normal Accident Theory

Normal Accident theory attempts to explain nature of accidents in complex systems. Its big insight is that accidents are normal, and best analyzed as recurring events. Other insights:

  • Redundancy can be a cause of error as much as a cure for it. Don’t make redundancy the default answer to safe design.
  • Move from “Oversight to Insight” where possible.
  • Centralization is necessary in tightly coupled systems, but not everything has to be centralized. Decentralization is a better fit for quick decision making.
  • Operator error is a lousy explanation for an accident in a complex system. Look at the system, not operators.
  • Close calls are useful as windows into “interactive complexity”.

More to be found on this NASA slideset: (pdf)


See also Three Dangers of Redundancy.

The last point seems to relate to Confession Inconsistencies. We don’t focus on the fact that something is wrong — that is bound to happen. But what do we learn from the *way* it went wrong that gives us insight into the larger system?

Command and Control details the history of near-accidents with nuclear weapons in the Normal Accident Theory framework.

Source: Normal Accident Theory


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