Vigilance in ATM

Vigilance in ATM


Vigilance is a term that refers to an individual’s ability to pay close and continuous attention to a field of stimulation for a period of time, watchful for any particular changing circumstances.

These changes may be quite small, but their potential effect may be considerable. The speed and accuracy with which we detect these changes (assuming we detect them at all) determines the timeliness of our decisions and actions. Vigilance is greatly affected by our level of alertness, and this is why we can be affected not only by being overloaded but also by being ‘under-loaded’.

Perception and vigilance are closely related and affect the accuracy and currency of our mental model of the air traffic situation. The vigilant ATCO can detect situations where a misperception is likely and will therefore be more likely to detect whether their perception is correct than a non vigilant ATCO.


Vigilance is not a skill; you cannot learn to be vigilant. Vigilance is a result of a number of circumstances over which the individual does not always have sufficient influence. It is also very difficult for the individual to detect changes in their vigilance. Even when feeling tired, we tend not to link that directly with a loss of vigilance. We easily overrate our capacity. Often, reduced vigilance is revealed by unwanted outcomes of decisions and actions. That is why it is very important that colleagues keep an eye on each other. It is usually easier for somebody else to notice when things start to deteriorate then it is for us. We can, however, take a number of measures that will help us to remain vigilant for a longer period of time. By making sure we are physically fit, well rested, well trained and informed, we enhance our capacity to stay vigilant longer.

Contributory Factors

Reasons for reduced vigilance include the following:

When the workload is very high, the ATCO’s attention is stretched and they are more likely to miss things. A similar situation can exist when the workload is very low, for example, during a quiet night shift. As a general rule, ATCO performance rises to a peak when the workload is high, but falls off if it becomes too high.

After a take over, the controller will start feeling confident after approximately 15 minutes. This can easily lead to a loss in vigilance and hence the chances of perception errors rise. Complacency is a much disputed term. It is sometimes argued that complacency can manifest itself as lack of vigilance; in particular, the ATCO may not crosscheck the situation sufficiently and may allow his mental picture to deteriorate so that an unsafe situation develops unnoticed. Such a situation can occur if automation is very good, because overconfidence in the system leads to complacency and lack of adequate vigilance.

Distraction or interruption is one of the most cited reasons for incidents. Some of the reasons for distraction or interruption can be due to non-essential conversation or extraneous noise (e.g. a radio or TV playing) and can severely impair a ATCO’s vigilance.

Fatigue affects vigilance in an insidious way. The ATCO may miss a potentially unsafe situation developing; for example, they may fail to notice an error made by a pilot or by themselves (e.g. an incorrect readback).


Solutions for supervisors and managers

  • Try to maintain an optimum level of vigilance within your team by continuous observation which will allow you to split or band-box sectors in good time.
  • Be aware of the fact that, in order to do your task, it is as essential to be vigilant as it is for an ATCO.
  • Give controllers training for low and “gear-shift” (e.g. sharp decline in traffic level) workload patterns over extended periods (e.g. > 2 hours).
  • Develop “defensive control” strategies and training.
  • Restrict unnecessary visitors, particularly in high workload or when training is being undertaken.
  • Make sure that controllers can not be distracted by activities such as watching television or listening to the radio in the ops room.
  • Make sure that all ATCOs receive adequate breaks during their period of duty.
  • Ensure that comfortable rest facilities are available, so that ATCOs can relax and refresh themselves between periods of duty.
  • Ensure that filtered water is available at all times in the operational environment. Hydration has a profound affect on vigilance. Coffee and tea act as dehydrators although do have a stimulant affect.

Solutions involving the team members

  • Try to avoid excessively high or very low workload by splitting or band-boxing in good time.
  • Be on your guard against complacency, especially when using high quality automation, to ensure that you are able to detect and act on any error or malfunction promptly, particularly when automation is affected by intermittent faults which are difficult to detect.
  • Do not allow yourself to be distracted by non-essential conversation or by extraneous noise. Speak up if these situations do occur and ask for the sources to be removed from the ops room.
  • Do not watch television in the ops room when colleagues are working within hearing or visual range of the TV.
  • Do ensure you have adequate sleep, especially before a period of night duty.
  • Do anticipate reduced vigilance brought on by fatigue; look out for the symptoms of tiredness and request a break.
  • Effective teamwork is often the only mitigation for vigilance errors - develop effective team resource management programs.

Further Reading


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