Free Accident Causation Theory and Incident Investigation Guidelines


  • To outline how accidents are caused.
  • To demonstrate the role of human error in accident causation.
  • To outline strategies for reducing human error.

Accident causation theory

Accident causation theory is the art and science that seeks to understand the deeper roots of why accidents happen. Understanding accident causation theory is essential in determining why workplace incidents occur and so that we can prevent re-occurrences. Through examples and case studies, students will gain an overview of the most important theories, strengths and weaknesses of each, and learn how to select the best theories and models to better understand why accidents occur.

Accident causation theory provides a systematic approach to the analysis of workplace accidents, to identify all potential root causes and to establish the links between workplace accidents and norms in workplace practice. It is an essential discipline that allows health and safety professionals to determine why workplace incidents occur, so that attention and energy can be applied to correcting deficiencies and preventing re-occurrences.

What causes industrial accidents?

Original theorists narrowed the cause of accidents to unsafe acts and unsafe conditions. This theory, which is still held by many regulators, business, labor unions and safety professionals, has been rightly criticized as oversimplified and one-dimensional. If we accept to any degree the notion that accidents are the result of human actions, we should apply a multi-dimensional accident causation model. This would encompass not just shop floor workers but the president and CEO and all other employees and management in between.

“Briefly sketch out the evolution of modern thinking about accident causation.”

Heinrich & the “Unsafe Acts” Theory

The original unsafe acts theory is most closely associated with Herbert William Heinrich and his famous 1926 report “The Origins of Accidents.” Heinrich analyzed 75,000 accident reports and concluded that 88 percent of all accidents are caused by the unsafe acts of persons, 10 percent by unsafe physical conditions and 2 percent by “acts of God.”

The Heinrich theory of unsafe acts and conditions dominated thinking about industrial accidents for decades. Heinrich and his advocates may have been correct in their observations, based on the information and research available to them at the time. But the world has changed considerably since Heinrich first propounded his theory.

Classification of Human Errors – Latent and Active Failures

  • Active failures these are the ‘errors’ made by operators/maintenance staff i.e. those with hands-on control of the system/equipment. They occur immediately prior to the accident event and are often seen as the ‘immediate cause’. Active failures are those errors which traditionally have been described as human error – driver error and pilot error being typical examples.
  • Latent Failures. These are decisions and actions that dormant in an organisation for some time until revealed by active failures. These are evident in poor procedures, poor design, inadequate training, poor attitudes to safety.

There are numerous topics and course considers the approaches and framework used to investigate accidents within a business management system context, and provides the learner with the tools, skills and knowledge necessary to investigate workplace accidents effectively.

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