Accident pyramid

Heinrich introduced the accident pyramid in his book. Industrial Accident Prevention A Scientific Approach. This pyramid illustrated his accident causation theory. Heinrich believed that unsafe acts led first to minor injuries and then over a period of time to a major injury event. The accident 

Heinrich introduced the accident pyramid in his hook Industrial Accident Prevention A Scientific Approach. This pyramid showed his accident-causation theory. Heinrich believed that unsafe acts led first to minor injuries, and then, over a period of time, to a major injury event. The accident pyramid proposed that 300 unsafe acts produced 29 minor injuries and one major injury. The concept of the accident pyramid remained unchallenged many years. However, some recent studies challenge the assumed shape of the equilateral triangle used by Heinrich. Some professionals now believe the actual shape of the model would depend on organizational structure and culture. 

Before we get started, we want to discuss your journey. Let s revisit the accident pyramid. You need a good understanding of what it takes to reduce incidents. This model will provide some useful information. We will discuss this concept again in Chapter 12, Conducting Effective Incident Investigations.  

In 1969, a study of industrial accidents was undertaken by Frank E. Bird, Jr., who was then the Director of Engineering Services for the Insurance Company of North America. He was interested in the accident ratio of 1 major injury to 29 minor injuries to 300 no-injury accidents first discussed in the 1931 book Industrial Accident Prevention by H. W. Heinrich. Since Mr. 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, Mr. Bird wanted to determine what the actual reporting relationship of accidents was by the entire average population of workers [6]. 

An analysis was made of 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. The study revealed the following ratios in the accidents reported  

Part of the study involved 4,000 hours of confidential interviews by trained supervisors on the occurrence of incidents that under slightly different circumstances could have resulted in injury or property damage. Analysis of these interviews indicated a ratio of approximately 600 incidents for every reported major injury [5]. 

Bird continues to say that, as we consider the ratio, we observe that 30 property damage accidents were reported for each serious or disabling injury. Property damage incidents cost billions of dollars annually and yet they are frequently misnamed and referred to as near-accidents. Ironically, this line of thinking recognizes the fact that each property damage situation could probably have resulted in personal injury. This term is a 

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Property damage and loss of production must also be considered in loss prevention. These losses can be substantial. Accidents of this type are much more common than fatalities. This is demonstrated in the accident pyramid shown in Figure 1-3. The numbers provided are only approximate. The exact numbers vary by industry, location, and time. No Damage accidents are frequently called near misses and provide a good opportunity for companies to determine that a problem exists and to correct it before a more serious accident occurs. It is frequently said that the cause of an accident is visible the day before it occurs. Inspections, safety reviews and careful evaluation of near misses will identify hazardous conditions that can be corrected before real accidents occur. 

Yet whilst Hollnagel (2014) warned of the allure of the graphical presentation that propelled the accident pyramid to its continued prominence in safety thinking (as discussed in Chapter 4), zero should arguably come with several warnings of its own the allure of the big round number, the allure of mathematics and measurement, and the allure of the snappy slogan - aptly illustrated in Figure 8.1. 

Why do some accident prevention professionals challenge the accident pyramid proposed by Heinrich ... 

Figure 5-3 Safety accident pyramid. Bird, Frank E., George L. Germain, Loss Control Management Practical Loss Control Leadership, revised edition. Figure 1-3, p. 5, Del Norske Veritas (U.S.A.), Inc., 1996. Adapted for use by Damon Carter.

When an incident occurs that results in an injury or in damage to property or equipment, we often find that the employees had been doing a particular job task the same way for a long time. This time luck ran out [5]. Refer to Chapter 5, Figure 5-3 to understand what is considered luck and then review the safety accident pyramid. 

The relationships shown and implied by the accident pyramid are simple, tempting and dubious. The two main problems have to do with the definition of the categories and the implied relationships among the categories. 

Despite Heinrich s caution, the accident pyramid is today commonly used as if it described different categories of events rather than different categories of outcome or injury. One reason for the different focus could be that today s systems have more layers of protection built in, which means that more events are stopped or caught before they can develop their final consequences. It therefore makes sense to look at the events rather than the outcomes. 

The four myths presented here (the causality credo, the accident pyramid, the 90 per cent solution, and the root cause) are of course not the only ones. Readers who are interested in other myths can quite easily find information in scientific papers and online... 

The result of the severity-level prognosis is directly dependent on risk parameters 0-, and Cj. In order to arrive at the severity levels, the distribution of the severity levels Se 1 to Se 4 is connected with a histogram typical for machine tools (i.e., accident pyramids of the BAuA). 

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