Hollnagel explains that the ideas behind ETTO are far from new. He was writing about the limitations of human resources and the need for trade-offs before he coined the term in 2001, and long before the publication in 2009 of Efficiency-Thoroughness Trade-Off: why things that go right sometimes go wrong.
In some ways, ETTO mirrors the UK's legal concept of reasonable practicability. As we saw in A is for ALARP (ioshmagazine.com/article/alarp) organisations can balance the degree of risk with the money, time or trouble of taking measures to avoid the risk (provided it is tolerable). ETTO describes the way individuals make this trade-off every time they carry out a task. Efficiency is defined as keeping the investment in resources -- time, materials, money, psychological and physical workload -- as low as possible, while thoroughness is carrying out an activity to achieve its objectives with no unwanted side-effects, such as accidents, injuries or damage.
If you think you are the sort of person who would never trade thoroughness for efficiency, think about how you park a car
Hollnagel's short explanation for ETTO is that "people routinely make a choice between being effective and being thorough, since it rarely is possible to be both at the same time. If demands for productivity or performance are high, thoroughness is reduced until the productivity goals are met. If demands for safety are high, efficiency is reduced until the safety goals are met." This sounds like a conscious choice, in which we understand a numeric target for safety and productivity and calculate the balance between the two. In reality, there is a feedback mechanism involved: if I burn or cut myself, I will take more care (become more thorough, less efficient) next time; if I miss my bus home, or get shouted at for taking too long on a job, I will endeavour to be more efficient (and less thorough) in future.
A simple example of the trade-off can be seen in a steady-hand game, in which a small loop of wire is manoeuvred over a complex, fixed wire shape, with the aim of ensuring the two do not touch. If they make contact, a buzzer sounds. The slower you move, the less likely you are to err. If there are time penalties for touching, with practice you would work out an optimum balance between efficiency (doing it quickly) and thoroughness (not triggering a buzzer): a three second penalty for racing through the tightest turn is better than taking ten seconds to prevent contact.
If you think you are the sort of person who would never trade thoroughness for efficiency, think about how you park a car. When the space is tight, you will spend longer optimising your distance from other cars to avoid damage when the other motorist returns; if you park in a wide driveway, you might reverse in quickly without too much thought for the precise location.
Similarly in the workplace the environment will influence the trade-off. If accuracy is praised and delays are of little concern, a worker can do things by the book; if adherence to procedures is not rewarded but finishing early is, efficiency will take the upper hand. Workers find a balance between the thoroughness (safety) and efficiency (getting the job done) through experimentation.
Safety professionals are not immune from the ETTO. In Barriers and Accident Prevention (2004) Hollnagel points out that we seek certainty over knowledge, giving accident investigation as another example of ETTO. To save time and effort it is easier to accept the first explanation that emerges, especially when it confirms prevailing beliefs. By accepting the first explanation we can re-create certainty quickly (even if we are wrong). It's easier to identify cladding as the sole "cause" of a building fire than to have to deal with the complexity of assessing the whole system of designing, building, maintaining and managing high-rise homes.
To avoid the errors that can result from a poor ETTO it is important that everyone understands those elements of the task that are essential and those that can be foregone in the name of efficiency. For routine activities this is straightforward. An over-long weekly checklist that includes an item for the presence of the no-smoking sign, along with the requirement to test the fire alarm, will tempt workers to ignore the whole checklist when time is short; distinguishing the "must dos" from the "nice to haves" will help workers to make the right ETTO. For complex activities Hollnagel presents a detailed solution to the ETTO problem in the form of FRAM (functional resonance analysis method) -- which conveniently gives us the next letter in our lexicon.