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Human errors

What are human errors

Human errors are incorrect performance of human actions. Humans are not made to do the right decisions in every case. Human errors can be divided into unintended- and intended human errors.

This database aims to give a general introduction into human errors and common human errors related to different life cycle phases of a product.

Unintended human errors

Unintended human errors can be defined as non-fulfilment of predefined tasks steps where the intention is fulfilment. Human errors could be wrong detection, wrong diagnosis or erroneous execution.

Wrong detection may be caused by:

  • Absent from place
  • Ambiguous information
  • Distraction (telephone…)
  • Failure to notice signal/alarm
  • Incorrect/incomplete recognition of state
  • Incorrect/incomplete recognition of value
  • Lack of attention
  • People see what they want to see
  • Reading wrong indication
  • Reading wrong value
  • Too low sound (out of normal physical limits)
  • Too much information (out of normal memory limit)

Wrong diagnosis may be caused by:

  • Misinterpreted symptoms
  • Misunderstanding (same word/different meaning – different words/same meaning)
  • Symptoms confused
  • Unfamiliar situation
  • Memory problems (to many alarms)
  • Unacceptable workload (to many diagnosis tasks at a time)
  • Missing information
  • Distraction
  • Situation conflicts

Erroneous execution of the action may be caused by:

  • Bad print quality
  • Bad communication
  • Conversion error
  • Complex action (out of normal evaluation capacity)
  • Lack of information
  • Misjudged operational mode
  • Too fast (out of normal physical limits)
  • Too heavy (out of normal physical limits)
  • Too little time (out of normal physical limits)
  • Reduced capabilities (tired, drunk,...)
  • Humans are trying to minimize their effort during a task
  • Humans are doing tasks giving recognition from other people
  • Humans are playing with technology they master
  • Humans may execute actions also when they are not supposed to
  • Human grasping refex when they are not supposed to

Erroneous execution can further be divided into three principal categories:

No action at all:
- The task is not done

Actions outside specified performance limits:
- The task is executed too fast
- The task is executed too slowly

Unintended action:
- The task is executed but at wrong time
- The task is executed but only a part is completed
- The task is executed but completely different than described

The above categories are directly comparable with “failure modes” for technical equipment, and can be used as a checklist for concrete human errors during an analysis. Human errors may take place during design, assembling, testing, transport, installation, operation and maintenance. Example of erroneous execution of tasks for specific lifecycle phases are:

Intended human errors

Human errors may also be intended. Examples of intended human errors are ignoring of tasks and execution of hostile actions.

Hostile actions

There are an increasing number of hostile human actions:

  • Criminality
  • Terror
  • Sabotage
  • Hacking

Protection against hostile actions is called security. Causes for hostile human actions may be complex, but is often an act of revenge for an unforgivable behaviour.

Ignoring tasks

There are several reasons for ignoring tasks.

1. Bad motivation

  • “So it normally is”
  • “It used to work before”
  • "Partly reading"
  • “Don’t care”
  • “I will not go and get that hammer I need (1 minutes walk) - I use the ax next to me instead”
  • "I am not interested to listen to your instructions"

2. Curiosity

  • “I wonder what happen if...”
  • "What is the limits for this technology (speed, loads, etc)"

3. Recognition

  • "Doing this will improve my reputation"
  • "Doing this will give me positive feedback from people I recognise"

4. Required improvisation

Another kind of ignoring is when the situation is such that the only way a task can be carried out effectively is to ignore certain rules. Personnel shortages, extreme weather conditions, equipment layout or design, equipment unavailability or the production pressure mean that the system will fail to meet its targets if the rules are followed. In this case, the personnel will be more aware they are taking risks than with routine ignoring. Supervisors will tend to ignore such violations since they too are aware of the need to ignore such rules if production targets are to be met. This type of violation is of specific interest in the offshore industry since lost time is very expensive.

Further discussion

The consequence of human errors depends on consequence reducing possibilities. Some human errors may result in situations that can be recovered easily by e.g. pushing another bottom. Other errors may have severe consequences. Human errors may also result in technical failures. It is claimed that more than half of all technical failures in operations where humans are involved are typically caused by human errors. Performance influencing factors are the reason for human errors. An introduction follow:

Updated: 07.01.2013

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