Human Factors - Fatigue

Fatigue is a physiological state of reduced mental or physical performance capability, resulting from sleep loss or extended wakefulness, that can impair alertness & ability to safely operate or perform safety related duties. There is in fact no universal definition of tiredness/fatigue, and its experience and perception are subjective. Whatever it’s source or nature, being fatigued seriously impairs our vigilance and judgement, especially in critical situations. The end result is a body that will not function unless revitalised by rest or nourishment.

Sleep is a natural state of reduced consciousness, involving changes in body & brain physiology in order to restore & replenish function. As a rule of thumb, people require 1 hour of good quality sleep for 2 hours of activity and a fully restorative sleep will last between 7-9 hours on average. Sleep efficiency (i.e. how fast you get to sleep) will dictate how much time in bed you require.

Caution is required in how fatigue is considered & managed. ‘Sleepiness’ is likely to be hugely under or mis-rated even from day one of sleep restriction and could result in harm. Ensure fatigue is considered at planning stage to identify risk points and raise awareness to allow recognition at all levels


Human Factors Forum - 08 June

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"For mitigation we must ensure that fatigue is considered at planning stage to identify risk points and raise awareness to allow recognition at all levels. You must consider how workload and schedules are reviewed / risk assessed with fatigue as a hazard and how you, as an individual manage work-life balance & flexible working. Document how you plan to counter any obstacles to objectives / workload, what training is required on burn-out & stress management, and, understanding the importance of sleep for safe operations."

Featured Resources

Human Factors Fatigue - Regulatory Requirements

Regulator Guide - Offshore

  • There should be a formal process for managing fatigue risk including management of working hours and any risk assessments required.
  • An assessment of fatigue risks associated with shift work should be carried out particularly when there are any changes to arrangements.
  • There should be clear approaches to managing fatigue risk including design of shift patterns, control of overtime and shift swapping, and provision of information to employees.
  • Working hours should be recorded and monitored through KPIs and the information should be used to identify any potential fatigue risk management issues.

Onshore COMAH

  • Not applicable


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