Part 5 - What causes 'human error'?

A number of factors can contribute to human error, a causative feature of accidents. These include:

1. Inadequate information

People commonly have understandable reasons for acting in the way they do. One common reason is ignorance of the processes in which they are involved and of the potential consequences of their actions due to not having sufficient information.

2. Lack of understanding

This often arises as a result of a failure to communicate. People make presumptions that certain actions have been taken when this is not the case.

3. Inadequate design

Designers of plant, processes or systems of work must consider human fallibility and the potential for human error. Where it cannot be eliminated, errors must be made evident or difficult. Systems should "fail to safety", that is, not operate in unsafe modes.

4. Lapses of attention

Lapses may be due to competing demands for attention and through distractions. The more monotonous and undemanding the task, the greater is the chance of these lapses.

5. Mistaken actions

This is the classic situation of doing the wrong thing under the impression that it is right. For example, the individual knows what needs to be done, but chooses an inappropriate method to achieve it.

6. Misperceptions

Misperceptions tend to occur when an individual's limited capacity to give attention to competing information under pressure produces 'tunnel vision'. There is a tendency to assume that an established pattern holds good so long as most of the indications are to that effect, even if there is an unexpected indication to the contrary.

One potent source of error in such situations is an inability to analyse and reconcile conflicting evidence deriving from an imperfect understanding of the task. Full analysis of the preventative measures required involves the need for people to understand the task as well as technical and ergonomic considerations concerned with the instrumentation and controls.

7. Mistaken priorities

An organisation's objectives may not be clearly conveyed to, or understood by, individuals. A crucial area of potential conflict is between safety and other objectives, such as output or the saving of cost or time.

Misperceptions may then be partly intentional as certain events are ignored in the pursuit of these competing objectives. When top management's goals are not clear, individuals at any level in the organisation may superimpose their own.

8. Willfulness

Willfully disregarding safety rules is rarely a prime cause of accidents. Sometimes, however, there is only a fine dividing line between mistaken priorities and willfulness.

For the potential for human error to be eliminated or substantially reduced, all the above factors need consideration. Training and supervision routines should take account of these factors.