ETTO Principle: Efficiency-Thoroughness Trade-off Hollnagel Professor Erik

Accident investigation and risk assessment have for decades focused on the human factor, particularly 'human error'. This bias towards the study of performance failures, leads to a neglect of normal or 'error-free' performance and the assumption that as failures and successes have different origins there is little to be gained from studying them together. Countless books and papers have been written about how to identify, classify, eliminate, prevent and compensate for it.

The ETTO Principle looks at the common trait of people at work to adjust what they do to match the conditions - to what has happened, to what happens, and to what may happen. Erik Hollnagel believes this assumption is false and that safety cannot be attained only by eliminating risks and failures. It proposes that this efficiency-thoroughness trade-off (ETTO) - usually sacrificing thoroughness for efficiency - is