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Accident Investigation and Root Cause Analysis

Accident Investigation and Root Cause Analysis

A step-by-step guide for accident investigation and root cause analysis. Accident and incident investigation explain why we should carry out incident investigation.

Explanation of Domino and multi-causality theories, immediate and underlying causes accident ratio studies and their limitations.

You can also download ‘Accident Investigation and Root Cause Analysis‘ PPT presentation and PDF from our books section. Which has option to download the following Accident investigation documents for free: Accident Investigation and Root Cause Analysis PPT presentation sample, Accident Investigation and Root Cause Analysis PDF book, Accident Investigation Form PDF, Accident Investigation Form DOCX, Accident Investigation Case Study

What is an “accident”?

An accident is an unexpected (or unplanned/unwanted) workplace event that causes injury or illness to an employee. An accident will disrupt the orderly flow of the work process. It involves the transfer of an excessive amount of energy due usually to the motion of people, objects, or substances.

Accident: an event that results in injury or ill health (provided in HSG245)

Occupational accident: An occurrence arising out of or in the course of work which results in: (a) fatal occupational injury; (b) non-fatal occupational injury. (provided in the 1996 ILO code of practice on the recording and notification of occupational accidents and diseases RNOAD):

Accidents just happen…don’t they?

Are they really unexpected or unplanned? If a company has 20 ‘lost time incidents’ in one year, and sets an objective to reduce the accident rate by 50% by the end of the next year, aren’t they planning 10 accidents for that year? If they reach that goal, will they be happy about it?

The only way to receive any benefit from accident investigation is to make sure root causes are uncovered and permanently corrected. This module will help you understand the simple – but important – steps in an effective accident investigation.

Although accident investigation is a valuable and necessary tool to help reduce accident losses, it is always considerably more expensive to rely on accident investigation than hazard investigation as a strategy to reduce losses and eliminate hazards in the workplace. In some cases, it may cost hundreds of thousands more as a result of direct, indirect and unknown accident costs.

But, when the accident happens, it happens and it’s important to minimize accident costs to the organisation. This can be done if effective accident investigation procedures are used.

So, let’s take a quick look at some basic concepts and then discuss the first steps to take in building an effective accident investigation programme.

Basic Theories of Accident Causation.

Accident causation models were originally developed in order to assist people who had to investigate occupational accidents, so that this could be done effectively.

Knowing how accidents are caused is also useful in a proactive sense in order to identify what types of failures or errors generally cause accidents, and so action can be taken to address these failures before they have the chance to occur.


The Domino Theory

In 1931, the late H.W. Heinrich presented a set of theorems known as ‘the axioms of industrial safety’. The first axiom dealt with accident causation, stating that ‘the occurrence of an injury invariably results from a complicated sequence of factors, the last one of which being the accident itself.’

Alongside, he presented a model known as the ‘domino theory’ as this accident sequence was likened to dominoes knocking each other down in a row.

The sequence is:-

  • Injury, caused by an
  • Accident, due to an
  • Unsafe act and/or mechanical or physical hazard, due to the
  • Fault of the person, caused by their
  • Ancestry and Social Environment.
Accident Investigation - Domino Theory

Accident Investigation – Domino Theory

The accident is avoided, according to Heinrich, by removing one of the dominoes, normally the middle one or unsafe act. This theory provided the foundation for accident prevention measures aimed at preventing unsafe acts or unsafe conditions.

The first update of the Domino Theory was presented by Bird & Loftus.

This update introduced two new concepts;

  • the influence of management and managerial error;
  • loss, as the result of an accident could be production losses, property damage or wastage of other assets, as well as injuries.

This model (known as the International Loss Control Institute or ILCI model) is shown in the figure below:

International Loss Control Institute or ILCI model

International Loss Control Institute or ILCI model

The domino model has been noted as a one-dimensional sequence of events. Accidents are usually multifactoral and develop through relatively lengthy sequences of changes and errors. This has led to the principle of multiple causation.

According to Peterson, behind every accident there lie many contributing factors, causes and sub-causes. The theory of multiple causation is that these factors combine together, in random fashion, causing accidents. So, during accident investigations, there is a need to identify as many of these causes as possible, rather than just one for each stage of the domino sequence.

The accident model is in reality an amalgam of both the domino and multi-causality theories, such as that shown below:


(Lack of Control)



  • cause a
  • cause b
  • cause c


  • cause d
  • cause e


  • cause f



All accidents, whether major or minor are caused. There is no such thing as an accidental accident. Very few accidents, particularly in large organisations and complex technologies are associated with a single cause. The causes of accidents are usually complex and interactive.

Multiple causation theory

This theory argues that for any single accident, there may be many contributing surface and root causes. This theory brings out the fact that rarely, if ever, is an accident the result of a single cause or act. Combinations of these give rise to accidents.

Multiple causation - accident investigation

Multiple causation – accident investigation

According to this theory, the contributing factors may include:

  • Environmental factors. Hazardous conditions in the workplace such as improper guarding, defective equipment, tools, equipment and machinery produced through inappropriate use and unsafe procedures.
  • Behavioral factors. Factors such as improper attitude, lack of knowledge, lack of skills and inadequate physical and mental condition. These “states of being” also represent hazardous conditions in the workplace. It’s important to understand that there are underlying causes for these behavioral factors. Management can have great influence over these factors.

Pure Chance Theory

According to this theory, every worker has an equal chance of being involved in an accident. Therefore, no single discernible pattern of events leads to an accident. All accidents correspond to “acts of God,” and no interventions exist to prevent them. This theory contributes nothing at all towards developing preventive actions for avoiding accidents.

Accident Proneness Theory

This theory says that there exists within a workplace a subset of workers who are more liable to be involved in accidents. Contradictory research and professional consensus does not generally support this theory and, if accident proneness is supported by any empirical evidence at all, it probably accounts for only a very low proportion of accidents.

Energy Transfer Theory

This theory claims that a worker incurs injury from exposure to a harmful change of energy. For every change of energy there is a source, a path and a receiver. This theory is useful for evaluating work for energy hazards and engineering control methods.

Accident causation

Many theories about the causation of accidents have developed over the years, some of which are very complex. Often, multiple causes can be identified. Using a fairly straightforward approach, the causes of accidents can be divided in two main types, ‘immediate’ or ‘primary’, and ‘indirect’ or ‘secondary’.

Immediate causes

Immediate causes of accidents can be due to unsafe acts and unsafe conditions.

Unsafe acts tend to be person-related, for example:

  • Failure to use personal protective equipment,
  • Leaving equipment in a dangerous condition,
  • Working without authority (e.g. no permit to work),
  • Horseplay,
  • Using equipment in the wrong way,
  • Failure to warn others of danger.

Unsafe conditions are due to environmental or organizational factors, for example:

  • Poor housekeeping,
  • Exposure to radiation,
  • Poor lighting or ventilation,
  • Badly-maintained equipment.

Unsafe acts and unsafe conditions usually need to coincide to result in an accident. An individual may act in an unsafe manner for a long time without an accident happening (the frequent comment following an accident is that it’s never happened before). Similarly, there could be an accident waiting to happen (unsafe condition), but good working practices have prevented it.

Indirect causes

Examples of indirect causes of accidents include:

  • lack of policies and procedures,
  • lack of training/supervision,
  • lack of resources,
  • Unsuitability of a person for particular task.

You can also download ‘Accident Investigation and Root Cause Analysis‘ PPT presentation and PDF from our books section. Which has option to download the following Accident investigation documents for free: Accident Investigation and Root Cause Analysis PPT presentation sample, Accident Investigation and Root Cause Analysis PDF book, Accident Investigation Form PDF, Accident Investigation Form DOCX, Accident Investigation Case Study

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