Loss Causation Theories

Loss Causation Theories

The basic duty of the safety officer at any workplace is to keep the record of the accidents and investigate them to ensure they don't occur again. In some countries it is legal requirement to report certain diseases and accidents. Sometimes, the information required to investigate the incident is not sufficient for investigation and there is no possibility to stop the reoccurrence using the available information. 

The basic and good starting point in any investigation is to consider two basic theories behind the accident occurrence.

1. Single Cause Domino Theory
2. Multi Causal Theory
3. System's Theory

Each theory is discussed below in details. Each theory describes how the accidents occur and how factors involved in an accident trigger a chain of events occurring one after another.

• Single Cause Domino Theory

In 1930, Herbert William Henrich (H. W. Henrich), an American Industrial Safety Engineer stated that;

"A Preventable accident is one of five factors in a sequence that results in an injury. The injury is invariably caused by an accident and the accident in turn is always the result of the factor that immediately precedes it".

The five factors from the Henrich's model are shown below;

Henrich’s Accident Model
Factor	Description
Ancestry & Social Environment	Undesirable traits of character e.g., stubbornness, greed, recklessness, that may be passed along through the inheritance. Environment in which a working is used to work, may develop undesirable traits of character or may interfere with education, Both inheritance and environment have ability to produce faults.
Fault of Person	Inherited or acquired faults constitute reason for committing unsafe acts or for the existence of mechanical or physical hazards.
Unsafe Act/ Mechanical Hazard/ Physical Hazard	Unsafe performance of persons such as standing under the lifted load, careless starting of machine, removal of safeguard, horseplay, mechanical hazards or physical hazards result in accident.
Accident	Events such as fall of person, fall of load onto the person stand underneath, hit by flying objects or moving machinery parts, such accidents occur.
Injury	Fractures, joint dislocation, cuts, etc., are the injuries which result directly from accident.

 

Henrich makes a vital point in his theory that the "A preventable injury is the natural culmination of a series of events or circumstances which occur in a fixed logical order".

For Example: 

If you put few dominos in a line one after another, and then push the one, it will cause the next one to fall and so on throughout the series. The chain of the events can be halted by removing the anyone domino.

In the same way, Henrich's model works, if one of these factors is eliminated and the occurrence of the injury can be prevented and accident will not take place. 

In these series of events, the most easiest factor that can be removed is the number 3, Unsafe Act/ Mechanical Hazard or Physical Hazard. 

Bird & Loftus

In 1976, Bird and Loftus extended the original Domino Theory presented by the H. W. Henrich and added the influence of the management in the cause and effect of accidents, suggesting a modified chain of events. 

Model of the Bird and Loftus included the following sequence;

1. Lack of controls by management.
2. This permits the existence of basic cause.
3. Basic cause leads to immediate cause
4. Later these are direct cause of accident
5. Final result is loss

• Multi Causal Theory

There may be more than one cause of an accident, not only in a series but occurring simultaneously. For example, a Methane (C4H4) requires following 3 elements; Methane Gas within explosive range of 5% to 15%, Oxygen and Ignition source. 

The ignition and explosion will occur only if these 3 are present together. The presence of each of these 3 elements in a workplace can be the result of any other event occurred earlier. 

In accident investigation, all causes must be investigated. Simple accidents have single cause that's the reason simple events occur more frequently. The severity of these events is minor to moderate. 

Catastrophic events involve multiple factors and has multiple causes that's why they occur rare but have catastrophic result. 

Multi Casual Theory also considers that there may be organizational, cultural, managerial, social causes that interact and lead to accident. This model is more complex than the single causal model and requires a lot of experience when investigating the cases. The investigation process becomes the complex too. 

Systems Theory

This is another way of looking at a multiple causal model. 

The process and factories can be assumed as a system, i.e., in an assembly plant, many parts and components are connected together to execute a job, with inputs and outputs in the presence of various control mechanisms. 

System approach is used to simplify the complex system and part of the system can be used as a black box. System failures are reduced with prevented or minimised with the help of components which can't fail, by installing backup system, and redundancy. 

Redundancy is putting extra components so that they takeover if the first one fails without interrupting the operation.

Failure of Multiple Causation Approach

These causes are divided into 3 further categories including Immediate Cause, Underlying Cause, and Root Cause, as well as Unsafe Act & Unsafe Condition is also discussed to check the reason behind any accident. 

The above mentioned theories can be combined with advance incident investigation techniques including Fall Tree Analysis, Event Tree Analysis, Root Cause Analysis etc.