Incidents & Accident Models

There are various models that emphasize different components that combined into an accident. While Heinrich’s Axioms of Industrial Safety are most widely applied, there are others that target relationships among the contributing factors to an injury. As a brief introduction, I’d like to share a few of our investigations and a model that aligns with them.

1) A man in the midst of a divorce was fatally injured by a backhoe driving with its bucket obscuring its line of sight along its path. The backhoe operator was new and relatively unfamiliar with it.

In Human Factors Theory, the decedent was likely unaware of his circumstances because of being overloaded with internal factors. The backhoe operator, on the other hand was overloaded with environmental & situational factors. Obviously, the operator required more rigorous training.

2) A lab worker using a drill press in a long-term, slow descent decided to rest weights on the handle controlling the press rather than continue the static activity after several days. She was complaining of shoulder pain. The worker was corrected, the drill press eliminated as a component of the experiment, and no incident occurred.

In Petersen’s Theory, the worker was caught in an ergonomic trap and made the decision to err based on logic. Her supervisors addressed the risk.

3) Multiple individuals were exposed to a cancer-causing substance without PPE. While PPE was not denied, it was not used by anyone including supervisors. While the containers were all individually labelled that PPE was required, no one took them seriously until one of the supervisors became ill.

In Epidemiological Theory, the situational characteristics and predisposition characteristics combined for a dangerous exposure.

4) Following a heavy rain, the roof of a warehouse gave way releasing a small swimming pool’s worth of water onto its contents. No one was injured. The cause of the build-up of water was determined to be the failure of the roof’s drainage system.

In Energy Release Theory, energy in the form of the weight of the pooling water was allowed to build up due to the structure of the roof and its failure of drainage. If the rain had not occurred at a sufficient rate that what minimal drainage that still functioned could manage it, then the energy would have been released slowly and controlled.

5) NOT one of our cases, but an ideal example:


In Systems Theory, worker, machine, and their surroundings function as a system. The more complicated the relationship, the more likely an incident. This is particularly important in the space program. As shown in the example, the curved pipe section interacted non-linearly (not predictably obvious) with the heating from the Sun, thus making its temporary support system unstable.

6) Combination Theory is the combination of all the applicable theories to an incident, including others not discussed above.