Incident Investigation 2: Immediate, Underlying and Root Causes
Scope of this domain
Domain 2 tests loss causation: separating immediate, underlying and root causes, and applying human-factors thinking rather than settling for blame.
Core rules
- Immediate causes are the unsafe acts and unsafe conditions at the moment of the event: an unguarded machine, an unsecured ladder, a person standing under a suspended load.
- Underlying causes are the failures that allowed those conditions: supervision, training, procedures, maintenance, purchasing, design, fatigue, production pressure.
- Root causes are management-system failures whose correction prevents recurrence, such as no procurement standard for access equipment.
- Use a human-factors lens: individual (competence, attitude, fatigue), job (task, workload, ergonomics, equipment) and organisation (culture, resources, priorities).
- Assume multiple causation. A single-cause conclusion usually signals a shallow investigation.
- Models help: Domino theory (remove a domino to break the sequence), Swiss-cheese/barrier model (holes in successive defences line up) and 5 whys to drill downwards.
Worked example
An operative falls from a ladder. Immediate: ladder not secured, only two points of contact. Underlying: ladder never inspected, user untrained, task rushed at shift end. Root: no ladder inspection regime and no purchasing standard for access equipment. Recommendations therefore target inspection, training and procurement, not just the individual.
Traps
Recording "carelessness" or "human error" as a root cause; stopping at the immediate cause; treating the last "why" as the root; recommending retraining for a problem created by design or supervision.