MODULE 6: EFFECTIVE INCIDENT / ACCIDENT ANALYSIS

Accident Causation Theories

Heinrich's Domino Theory

In 1931 W.H. Heinrich developed the domino theory, which argues that 88% of all accidents are caused by unsafe acts of people, 10% by unsafe actions and 2% by "acts of God". He believed a five-step accident sequence occurred in which each factor would actuate the next step just like we see in a row of falling dominoes. The sequence of accident factors were:

  1. ancestry and social environment
  2. worker fault
  3. unsafe act together with mechanical and physical hazard
  4. accident
  5. damage or injury.

He believed that by removing a single domino in the row the sequence would be interrupted, thus preventing the accident. The key domino to be removed from the sequence, according to Heinrich was domino number 3. It's surprising how firmly this theory took hold in the safety profession given that he provided no data for his theory.

 

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