There are almost as many theories about the causes of accidents as there are definitions of what constitutes an accident. It is difficult to determine if any of these theories has had a profound impact on accident prevention.
This is probably the earliest of the derived theories and is still commonly found in certain sectors of management. This theory assumes that the fault of the individual was the sole cause of the accident.
These theories centre around accident causation being a result of either unsafe acts or unsafe conditions, or sometimes both.
There are a number of theories of this type; the following are examples.
The domino effect theory: in a sequential combination of five factors (social environment, human error, unsafe acts, accident, injury), each of the factors alone will not cause an accident so that removing any one would be effective in accident prevention; however, each of the factors can be depicted as a “domino” — when one falls down the others following it also fall down.
Where the accident is seen as a sequence of events involving immediate, basic and underlying causes (lack of control). Consider an accident where an employee falls over a cable that was trailing across a floor. Immediate causes are those identified at the time of the accident and equate to the unsafe acts or conditions existing immediately prior to an accident, e.g. the cable stretched across the floor. Basic causes are those that caused the cable to be there, e.g. the plug socket being too far from the equipment used. Underlying causes relate to management/social factors where a lack of control allowed the design of the room and the use of the equipment to come about in such a way that it was possible for the basic and immediate factors to occur, which in turn gave rise to the accident.
These are also called “multi-causal theories” and believe three major types of factor interact to give rise to any accident. An accident can occur in a situation where less than adequate performance in a number of the factors combine together to create an unsafe situation.
The factors are based on: decision makers, line management & preconditions.
Multi-causal theories often use tree diagrams. Careful use of this technique can ascertain the direct causes, indirect causes and underlying factors that contribute to the accident. The technique known as MEEP is a common approach when pinpointing these underlying factors. This involves identifying: the materials involved; the equipment used; the work environment; and the people involved.
Dr James Reason’s “Swiss Cheese Model of Accident Causation” (also known as the cumulative act effect) is a recent theory that suggests that systemic failures, or accidents, occur from a series of events at different layers of an organisation. This model posits that a system is similar to slices of Swiss cheese. There are holes in it that represent opportunities for failure, and each slice is a layer of the system. When holes in the layers line up, a loss (or accident) occurs. Each layer of the system is an opportunity to stop an error; the more layers, the less likely an accident is to occur. The major layers of a system are: unsafe acts, conditions (for unsafe acts), unsafe supervision, and influences of an organisation.
It should be noted that multi-factorial theories are currently very influential in many aspects of risk management and can be applied to wider range of scenarios other than just accidents and near misses.
More recent theories on health and safety management in general have centred around the idea that accident prevention is really a function of management and that management has to be systematic. This is also linked to the idea that understanding culture is an important element. The culture of an organisation should be developed and influenced to secure safety as an intrinsic part of the organisational culture. The systems theories view accident causation as being a result of complex system interactions.
An accident then becomes of interest because it demonstrates that there has been some system failure which has exposed the organisation to some risk. Failures in health and safety are largely attributable to organisational factors, i.e. the culture, management style and general climate of a workplace are largely responsible for success and failure in health and safety. Also, the majority of accidents have a behavioural element. This is an extension of management responsibility.
If the management systems were working properly then the organisational rules should have been effective. If the rule has failed (and somebody ignoring the rule must be seen as a failure of the rule itself) then the management systems that designed, maintained or reviewed the rule were inadequate.
The link of accident causation to management systems approaches is made by the consideration of the fallible decision-making processes of management. Some decisions will not be the right ones, either because of lack of knowledge or because of conflicts of interest (e.g. production goals versus safety goals).
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