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Tripod Beta

Posted on November 19, 2012 in Articles

Accident investigator experts have concurred that 80% of the accidents lies on the Human Factor.   The realm of human factors is complex and incorporates many disciplines such as psychology, physiology, sociology, biomechanics, systems science, and management science.  In simplifying human factors for incident investigation, James Reason’s “Swiss Cheese” model of human error has been specifically used to determine the failed or missing barriers, Figure 1.
Swiss Cheese Model

Incident investigation tool, Tripod Beta enables in-depth analysis by looking into the “holes in the cheese”.  It encompasses the chain of events, barriers that should have stop them and failure for each of the barriers. 

The investigation starts with the incident and investigators work towards the root cause(s) of the incident.  As shown in Figure 2, the incident is primarily caused by the unsafe act or inaction of personnel at work, known as Active Failure(s).  Active Failure in turn is caused by Precondition(s) such as environmental, situational or “psychological” states.  Finally, the underlying or root cause(s) is/are found in the organisational deficiency where the Latent Failure resides.

Investigation flow
The concept of Tripod comes from the “tree diagram” (also known as Tripod Trio’s) representation of the incident mechanism which describes the events and their relationships, Figure 3.  The event or incident happens when the Hazard meets the Object. In basic operational control, there will be barrier(s) to prevent this.

Tripod Beta - Tree Diagram
Tripod Beta focuses on the reasons for the failure of the barrier and development of actions addressing the underlying causes.  The analysis works in three basic steps (Figure 4):

1.    What happened?  What was the incident?
       Use Tripod Trio’s.

2.    How did it happen?  What barriers failed?
       Conduct barrier analysis.

3.    Why it happened?  What caused these barriers to fail?
       Apply causation paths.

Tripod Beta Investigation Process
Tripod Beta provides an organised and systematic approach in incident investigation process.  Ending at the organisation deficiency, the incident is prevented from recurrence effectively.


Note:  Basic Risk Factors are the dimensions of working environment, e.g. Design, Training, Communication, Incompatible goals, Organisation, etc.

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