A Causation Model for Hazardous Incidents

Article excerpt

What are the factors that contribute to a hazardous incident? A distinguished safety professional offers a model that can be used to understand this most basic occupational safety question.

For the practice of safety to be truly professional and effective, it must have a sound, valid and generally accepted hazards-related incident causation model. As Dr. Roger L. Brauer, executive director of the Board of Certified Safety Professionals, has commented: "Good science requires that safety professionals do the validation work necessary to prove that what they propose, based on the causation models they have adopted, is effective and that real risk reduction is achieved."

Brauer's statement is significant. We must validate our concepts, and what we propose must be effective in achieving risk reduction. To promote discussion toward arriving at an accepted causation model, I present a model (Figure 1) that can be validated, conceptually.

At least 25 causation models are referenced in safety literature. Since they present a great diversity of thinking, all of them cannot be valid. Some of the work done by safety professionals, based on flawed causation models, is misdirected and ineffective. Safety professionals who investigate a given hazards-related incident should identify the same causal factors, with minimum variation. That is unlikely if their understanding of incident causation and the thought processes they apply have different, even contradictory, foundations.

Several authors have recognized the absence of, and the need for, a generally accepted accident causation model. Robert E. McClay, in his paper Toward a More Universal Model of Loss Incident Causation(1) stated: "The most obvious example of a weakness in the theoretical underpinning of Safety Science is the lack of a satisfactory explanation for accident causation. ..." And Ted S. Ferry, in Modern Accident Investigation and Analysis(2), observed: "The scientific literature on mishap analysis offers little insight into the process by which mishaps occur."

Assumptions Made

This incident causation model is based on the following set of ideas:

1) Occupational injury and illness risk levels are determined primarily by an organization's culture.

2) Management commitment (or noncommitment) to safety is an extension of an organization's culture, and is the source of the management decision-making affecting the avoidance, elimination or control of hazards.

3) A practice of safety based on a causation model that focuses on unsafe acts of workers as the principal causal factors will be ineffective in relation to the reality of causal factors.

4) A causation model for hazards-related incidents should emphasize the origins of decision-making, rather than outcomes such as human error.

5) A large majority of the problems (incident causal factors) in an operation are systemic and derive from the workplace and work methods created by management; and responsibility for the small remainder of the incident causal factors lies with the worker. (Extrapolated from Out of the Crisis(3) by W. Edwards Deming.)

6) Causal factors derive from those less than adequate policies, standards, procedures and accountability systems, or their implementation, that impact on design management, operations management and task performance.

7) Design management, operations management and task performance aspects of causal factors are interdependent and mutually inclusive.

8) Unwanted energy releases or exposures to hazardous environments are necessary to the occurrence of hazards-related incidents.

9) Hazards-related incidents, even the ordinary and frequent, are complex and have multiple and interacting causal factors.


Incidents encompass all hazards-related events that have been referred to as accidents, mishaps, near-misses and occupational illnesses. All incidents to which this applies derive from hazards. …