Incident triangle dispute: not accurate, but true

From Dennis Windt; Henrich’s incident triangle dispute on severity rates is not necessarily accurate, but raises awareness in safety practice.

The incident severity correlation triangle of Heinrich, popularsised by Frank Bird as the ‘Bird Triangle’, highlighted the importance of risk sources or incident root causes. Bird was trying to instill a sense of pro-activeness to industry.

In response to the post on, revealing that Heinrich never revealed his research finding, and probably sucked the numbers out of his thumb, do we have an alternative model? In my opinion, safety and incident rating is detrimental to the cause of safety.

Incident rates encourage incident hiding, to obtain and maintain good ratings and ‘improvement’, but in fact it hides incidents and thus hides safety management problems.

Incident rates perpetuate window dressing. What is the good of telling people what has happened, as opposed to attempting to ‘uproot’ root causes in a proactive fashion, to eliminate whatever you humanly can in an attempt to avoid fate?

Trying to beat death is not predicted by time, until time runs out! That is how I interpreted the Frank Bird [based on Heinrich] triangle, and I recommend it to leaders in business.

Myth could be true

But different strokes for different folks. It is easy to criticise something without offering constructive alternatives in turn, so with all due respect, until we have another solution, Frank Bird is still the man?

Many myths, fairy tales and fables are used as ways to bring awareness of potential problems of various degrees to an audience that are, at most, not aware of their existence but often surrounded by them daily.

In an ideal world, Goldylocks is a criminal, but in present times she could be a president. In some religious orders, she may well rule the world for a spell in the future.

If told properly with the father bears’ roars of disapproval at an intruder tampering with his belongings and sampling his meal, Goldylocks would awaken from her slumber and would flee in terror, never to set foot on premises that do not belong to her ever again.

This may also keep her from wandering off the familiar path. A valid lesson for anyone’s child in this day and age. Myths often have great value.

Call for alternative stats models

Editor comments; We invite readers to post more alternative severity versus frequency models here.

Severe effects are generally fewer than minor effects, but severe effects do not require major incidents, and minor effects could follow major incidents.

One alternative incident severity numbers model is that larger numbers are more predictable, and smaller numbers are more erratic, therefore an operation could run for years without lot time injuries, then sustain a number of deaths, or could seriously injure many workers without causing deaths.

The ‘traditional’ Heinrich triangle is not valid, and is misleading in its deceptive logic that it applies to all workplaces. Much depends on what is counted as an incident, and what is considered severe.

Mining kills many workers prematurely due to a combination of silicosis, lifestyle choices, lifestyle options, labour sending areas living conditions and state services, while workplace incidents are arguably few and the consequences accounted to be relatively light.

We think by perception as much as by ‘fact’, but are these elements subject to patterns that have been fixed to absolute, calculable values? Taking risk and negotiating quality of life, and life itself, against perceived gain, remains a human value.

Extract of disputed ‘statistical findings’
Here is an extract from one of the thousands of blogs based on the Heinrich and Bird incident states triangle, the basis of which is disputed since Heinrich’s study could not be replicated, except by Bird, and his data sources could not be found:
“Since Heinrich estimated this relationship and stated further that the ratio related to the occurrence of a unit group of 330 accidents of the same kind and involving the same person, Bird wanted to determine what the actual reporting relationship of accidents was by the entire average population of workers.

“HW Heinrich’s classic safety pyramid is now considered the foremost illustration of types of employee injuries. [disputed]. There Bird analyzed 1,753,498 accidents reported by 297 cooperating companies. These companies represented 21 different industrial groups, employing 1,750,000 employees who worked over 3 billion hours during the exposure period analyzed…
“• For every reported major injury (resulting in fatality, disability, lost time or medical treatment), there were 9.8 reported minor injuries (requiring only first aid). For the 95 companies that further analyzed major injuries in their reporting, the ratio was one lost time injury per 15 medical treatment injuries.
“… 30.2 property damage accidents were reported for each major injury.
“…approximately 600 incidents for every reported major injury.
“In referring to the 1-10-30-600 ratio in a pyramid it should be remembered that this represents accidents reported and incidents discussed with interviewers, and not the total number of accidents or incidents that actually occurred.
“…each property damage situation could probably have resulted in personal injury. This term is a holdover from earlier training and misconceptions that led supervisors to relate the term “accident” only to injury.
“The 1-10-30-600 relationships in the ratio indicate clearly how foolish it is to direct our major effort only at the relatively few events resulting in serious or disabling injury…”

All of the above has since been disputed and could be considered unproven, and partly due to false data, false deductions, and false reasoning, although the relative numbers of recognised incidents and acknowledged severity or cost seems to correlate inversely, that is, cheaper incidents are more common, while costly incidents are more rare. -Editor

IMAGE; One of hundreds of incident numbers versus severity correlation pyramids based on Heinrich’s study, considered to be false and misleading in more recent academic studies.

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One thought on “Incident triangle dispute: not accurate, but true

  1. If the numbers are suspect, then we could compare stats with a known industry that has readily available data.
    We could use insurance data for traffic accidents over a set period and analyse that data. The 1:10:30:600 principal will either hold true statistically, or it will show that the original data set of Bird [Henrich], if there was any, just represents averages of multiple industries, which by itself skews the numbers and allows for manipulation.

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