Heinrich Triangle Theory

The Heinrich Triangle Theory, also known as the Accident Triangle or Safety Triangle, is one of the most influential theories in occupational health and safety.

Proposed by Herbert W. Heinrich in his 1931 book Industrial Accident Prevention: A Scientific Approach, the theory suggests a functional relationship between the number of near-misses, minor injuries, and major fatalities.

The Core Ratio: 1–29–300

Heinrich’s research, based on the analysis of over 75,000 insurance claims and accident reports at Travelers Insurance Company, led him to propose a specific ratio:

1 Major Injury (Fatality or serious disability): At the top.

29 Minor Injuries (First-aid cases or cuts): In the middle.

300 Near-Misses (Accidents with no injury): At the base.

The Logic: Heinrich argued that for every major injury, there are hundreds of precursor events (near-misses). If you focus on reducing the frequency of the "minor" incidents at the bottom of the triangle, you will mathematically reduce the probability of the "major" injury occurring at the top.