Getting to grips with the human factor
Performance levels
Now we come to the scientific bit. Error types can be classified at three levels:
- At the skill-based level, we carry out routine, highly-practised tasks in a largely automatic fashion, except for occasional checks on progress. This is what people are very good at for most of the time.
 We switch to the rule-based level when we notice a need to modify our largely pre-programmed behaviour in line with some change in the situation around us. This problem is often one that we have encountered before and for which we have some pre-packaged solution. It is called rulebased because we apply stored rules of the kind: if (this situation) then do (these actions).
- The knowledge-based level is something we come to very reluctantly. Only when we have repeatedly failed to find a solution using known methods do we resort to the slow, effortful and highly errorprone business of thinking things through on the spot. Given time, trial and error learning can often produce good solutions. In an emergency however, because consciousness is also very limited in its capacity to hold information, usually not more than two or three distinct items at a time, our brain behaves like a sieve, forgetting some things as we turn our attention to other matters. In addition, we can also be plain scared, and fear (like other strong emotions) has a way of replacing reasoned action with ‘knee-jerk’ or sometimes over-learned responses.
Classifying violations
Case and field studies suggest that violations can be grouped into four categories namely: routine violations, optimising violations, situational violations and exceptional violations. The relationship of these to both the performance levels and error types is summarised in the table below with definitions following:
Routine violations – almost invisible until there is an accident (or sometimes as the result of an audit), routine violations are promoted by a relatively indifferent environment; i.e. one that rarely punishes violations or rewards compliance – “we do it like this all the time and nobody even notices”.
Optimising violations – corner-cutting; i.e. following the path of least resistance, sometimes also thrill seeking – “I know a better way of doing this”.
 Situational violations – standard problems that are not covered in the procedures – “we can’t do this any other way”. An excellent example concerns railway shunters: the rule book prohibits shunters from remaining between wagons when wagons are being connected. Only when the wagons are stopped can the shunter get down between them to make the necessary coupling. On some occasions however, the shackle for connecting the wagons is too short to be coupled when the buffers are fully extended. The job can only therefore be done when the buffers are momentarily compressed as the wagons first come in contact with each other. Thus the only way to join these particular wagons is for the shunter to remain between them during the connection. The result can be fatal.
Exceptional violations – unforeseen and undefined situations – “now this is what we got trained for”. A simple example on an oil-rig illustrates the point: a pair of engineers were inspecting a pipeline. One of them jumps into an inspection pit and is overcome by hydrogensulphide fumes. His companion fully trained to handle such situations raises the alarm but then jumps down to help his partner, whereupon he too is overcome. Exceptional violations often involve the transgression of general survival rules rather than specific safety rules. Survivors of such exceptional violations are often treated as heroes. Exceptional violations can also be seen as an exercise of initiative even sometimes provoking reward if, that is, you get away with it!
Given that human beings are able to circumvent both controls and defences with sometimes quite remarkable cunning, the problem can be summed up as follows:
Finally there is the theory of sheep and wolves. Studies have identified two sorts of people – sheep and wolves. Wolves accept rule violation as a norm, sheep do not. This results in:
- Sheep in sheep’s clothing
- Wolves in wolf’s clothing
- Sheep in wolf’s clothing
- But the largest group are wolves in sheep’s clothing – they haven’t violated the rules. Yet!
Accidents
An accident or incident is an unplanned chain of events which has, or could have, caused injury or illness and/or damage to people, assets, the environment or reputation. Modern research has shown that the basic components of an accident can be shown as the simple ‘formula’:
And that by adding the concept of breached, or missing, controls and defences a simple accident can be shown diagrammatically:
But accidents are not as simple as this, because usually there are several breached or missing controls and defences. More importantly almost all accidents consist of a series of interlinking ‘events’, in which each event becomes either a new hazard or a new target in its own right. In the presence of further targets or hazards and new and further breaches of
defences and controls, a second event is created and so on. During accident investigations it is not uncommon to identify five, six or even seven interlinking events before the final event or accident becomes a reality.
The concept of the ‘event chain’ or ‘incident trajectory’ is shown in the diagram below:
Note the original (first) event resulted in a fire. In the presence of two new ‘targets’, i.e. an operator and a piece of equipment, the resultant double event led to a badly burnt operator (injury) and damaged equipment (asset damage). Because the immediate aftercare of the injured operator (first aid or paramedic treatment) was ineffective (new hazard), the operator’s
injuries resulted in a partial disability (final event).
Reverting to the simple accident diagram and the ‘formula’ in the text box on the facing page, if one of the controls or defences had not been breached there would not have been an accident. If detected the resultant ‘near-miss’ or ‘dangerous occurrence’ could still have been reported, investigated and acted upon as if it were the real thing.
The usual mechanism, whereby controls and defences are breached, is an unsafe act by an individual at the sharp end. Occasionally, they may be breached by an inherent unsafe condition but these too will invariably have been caused by the acts or omissions of people, which may be nothing more than a simple and unintentional mistake. As has already been
mentioned, such unsafe acts or unsafe conditions are generally referred to as active failures.
While active failures are interesting – indeed much can be learnt from them – a lot more can be learnt, and more effective remedial measures put in place, by addressing the sick camel in the first place.
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