Heinrich’s domino theory

A classic incident theory is H.W. Heinrich s domino theory of causation, which has had a significant influence on practical incident investigation. (2) Many adaptations of Heinrich s original proposal have been developed by later researchers. Heinrich labeled his five dominoes as follows ... 

The two key points in Heinrich s domino theory are that (1) injuries are caused by the action of preceding factors, and (2) removal of the events leading up to the incident, especially employee unsafe acts or hazardous workplace conditions, prevents accidents and injuries. Heinrich believed that unsafe acts caused more accidents than unsafe conditions. Therefore, his philosophy of accident prevention focused on eliminating unsafe acts and the people-related factors that lead to injuries (Brauer, 1990). 

Figure 5-2. An illustration of Heinrich s Domino Theory of Accident Causation.

The first steps in being able to prevent accidents from propagating is to understand the combination of factors that can initiate them, and what causes them to escalate [Ontario 1999]. The generally accepted theories of accident causation, for example Heinrich s domino theory [Heinrich 1931] and Reason s organisational accident theory [Reason 1997] may use different terminology, but they do all have common themes ... 

According to Heinrich s early theory, the following five factors influence all accidents and are represented by individual dominos ... 

Heinrich advocated a multidisciplinary approach to safety, focused on engineering, psychology, management, and salesmanship. The emphasis on psychology supported his theory that the majority of accidents were caused primarily by the unsafe acts or behavior of employees— the axiom on which his prevention philosophy was based. This axiom was central to Heinrich s domino model of accident causation, which depicted five dominos lined up in a sequence. As we discussed in Chapter 12 (Figures 12-7 and 12-8), unsafe acts/conditions were placed in the central position, preceded by inherited or acquired personal faults, and followed by an inci-... 

Heinrich s approach is to identify, evaluate, and work on the middle dominoes, not just the last one or two dominoes in the line. The domino theory has significant limitations. The basic assumption is that there is a linear relationship between causation and progression. In other words, one occurrence follows another and ends in an incident. In the context of process-related incidents, this assumption is not always valid. Often parallel occurrences coincide to result in an incident rather than occurring as purely sequential occurrences. Nevertheless, the domino theory can provide a useful conceptual framework for simple incidents. 

The origin of the Domino Theory is credited to Herbert W. Heinrich, circa 1931, who worked for Travelers Insurance. Mr. Heinrich nndertook an analysis of 75,000 accident reports by companies insnred with Travelers. This resulted in the research report titled The Origins of Accidents, which concluded that 88 percent of all accidents are caused by the unsafe acts of persons, 10 percent by unsafe physical conditions, and 2 percent are Acts of God. His analysis of 50,000 accidents showed that, in the average case, an accident resulting in the occurrence of a lost-time work injury was preceded by 329 similar accidents caused by the same unsafe act or mechanical exposure, 300 of which produced no injury and 29 resulted in minor injuries. This is sometimes referred to as Heinrich s Law. Mr. Heinrich then defined the five factors in the accident sequence, which he identified as the Domino Theory. Heinrich s work is the basis for the theory of behavior-based safety, which holds that as many as 95 percent of all workplace incidents are caused by unsafe acts. See also Accident Chain Behavior-Based Safety. 

In 1986, Frank Bird and George Germain [1] used Heinrich s [4] model to develop another accident causation model (Figure 12-8). This model used the same domino theory to show its key concepts of loss control. 

The domino theory of injuries listed five steps that lead to injury. In was first the environmental and social climate and ancestry that allowed the second step of human error to develop. This error in turn led to unsafe acts or mechanical and physical hazards. These acts or hazards then allowed an accident to occur, and then some accidents produced injury. Undesirable human traits such as nervousness were either inherited or created and exacerbated by their environment. These traits created human faults that then allowed unsafe acts such as not wearing protective gloves, or even engineered oversight of the need for machine guarding (Heinrich et al., 1980). Dr. Haddon was removing the fifth step of injury occurrence. Today s efforts of ergonomic control also attempt to remove the possibility of an error as well. 

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