DOE’s core analytical techniques 5

4.1.5 Root cause analysis

Root cause analysis is any analysis that identifies underlying deficiencies in a safety management system that, if corrected, would prevent the same and similar accidents from occurring. Root cause analysis is a systematic process that uses the facts and results from the core analytic techniques to determine the most important reasons for the accident. While the core analytic techniques should provide answers to questions regarding what, when, where, who, and how, root cause analysis should resolve the question why. Root cause analysis requires a certain amount of judgment.

A rather exhaustive list of causal factors must be developed prior to the application of root cause analysis to ensure that final root causes are accurate and comprehensive.

One method for root cause analysis described by DOE is TIER diagramming. TIER-diagramming is used to identify both the root causes of an accident and the level of line management that has the responsibility and authority to correct the accident’s causal factors. The investigators use TIER-diagrams to hierarchically categorise the causal factors derived from the events and causal factors analysis.

Linkages among causal factors are then identified and possible root causes are developed. A different diagram is developed for each organisation responsible for the work activities associated with the accident.

The causal factors identified in the events and causal factors chart are input to the TIER-diagrams. Assess where each causal factor belong in the TIER-diagram. After arranging all the causal factors, examine the causal factors to determine whether there is linkage between two or more of them. Evaluate each of the causal factors statements if they are root causes of the accident. There may be more than one root cause of

a particular accident.

Figure 13 shows an example on a TIER-diagram.

Tier

Causal Factors

Root causes (optional column)

Tier 5: Senior Root cause # 1 management

Tier 4: Middle Root cause # 2 management

Tier 3: Lower management

Tier 2: Root cause # 3 Supervision

Tier 1: Worker actions

Tier 0: Direct cause

Figure 13. Identifying the linkages to the root causes from a TIER-diagram.