Theories / Models & Use of Loss Causation Techniques Flashcards
F.E. Bird used accident data to product an accident triangle to conclude there appears to be a relationship between the numbers of different types of accidents.
Outline the contents of the accident triangle
1 Serious or disabling injury
10 Minor injuries
30 Damage accidents
600 Accidents with no damage
Explain the limitations of accident triangles
Not every near miss or minor incident involves risk which could actually had led to a serious incident
Care required when comparing triangles due to there being different triangles, different definitions and different industries
Statistical significance - you need a certain amount of representative data for a meaningful comparison.
What are the five factors in Heinrich’s single-cause domino theory?
Ancestry & Social Environment
Undesirable traits of characteristics
Fault of Person
Inherited or acquired faults of person i.e. temper, recklessness, excitability
Unsafe Act and/or Mechanical or Physical Hazard
Unsafe performance of persons
Accident
Events such as falls, striking etc.
Injury
Fractures, lacerations etc.
Explain the major point in Henrich’s theory
A preventable injury is the natural culmination of a series of circumstances which occur in a fixed logical order.
Explain what Bird & Loftus did with the single-cause domino theory?
Bird & Loftus extended Heinrich’s theory to take into account the influence of management in the cause of accidents.
What are the five factors in Bird & Loftus single-cause domino theory?
Lack of control by management
This permits the existence of basic causes
In turn, this leads to immediate causes
These are subsequently the direct cause
Finally, this results in the injury
What is meant by Multi-Causal Theories?
There maybe one cause of an accident, not only in sequence, but occurring at the same time. For example a methane explosion requires methane in the explosive range of 5% to 15%, Oxygen or air and an Ignition Source.
What is meant by a Systems Theory?
This is another way of looking at a multiple-cause situation.
Factories and processes can be viewed as systems i.e. an assembly of parts or components connected together in an organised way to perform a task, with inputs and outputs and various kinds of control mechanisms.
A systems approach is often useful in simplifying complex operations.
System failures are prevented or minimized by components which cannot fail, by backup systems, or by redundancy built into the system. Accidents happen in our system because it includes fallible components, such as machines and human beings. The system is operating in the failure mode.
What is an immediate cause of an accident?
An immediate cause refers to the direct cause of the accident i.e. the actual agent of injury or damage such as the sharp blade of the machine.
What is an underlying or root cause of an accident?
Underlying or root causes are the less obvious systemic, or organisational reasons for the incident
What is the meaning of an unsafe act?
An unsafe act is human performance which is contrary to accepted safe practice and which may, leads to an accident.
What is the meaning of an unsafe condition?
Unsafe conditions are basically everything that is unsafe after you take away unsafe acts.
Explain Reason’s model of accident causation
Following research into a series of disasters, James Reason has developed a model of accident causation for organisational accidents. An organisational accident is rare, but if it happens often has disastrous consequences.
Reason’s model shows that organisational accidents do not arise from a single cause but from a combination of active and latent failures.
In the model there is a series of defence barriers between the hazard and a major incident. These not only prevent the incident but also provide warning of danger and mitigate the consequences. These multiple layers characterize complex technological systems, such as a chemical plant.
However, the barriers are not perfect and can be defeated.
What is meant by an active failure?
Active failures are one cause for the barriers to be defeated.
Active failures are those unsafe acts which have immediate effects on the integrity of the system and are usually committed by those directly involved in the task.
What is meant by a Fault Tree Analysis?
A fault tree analysis is one analytical technique for tracing the events which could contribute.
The fault tree is a logic diagram based on the principle of multi-causality, which traces all branches of events which could contribute to an accident or failure.
An FTA is drawn from the top down. The starting point is the undesired event of interest. You then have to logically work out the immediate and necessary contributory fault conditions leading to that event. These may each in turn be caused by other faults and so on. Each branch of the tree is further developed until a primary failure (such as a root cause) is identified.
