Section 9.4

Factors Affecting Performance

Fitness/health, stress, time pressure and workload, sleep and fatigue, alcohol/medication/drug abuse.

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Main ideas

Fitness and health (illness, medication side effects) reduce alertness and reaction time — self-certifying "fit for duty" before a shift is a real human factors control, not a formality.
Stress — both domestic and work-related — narrows attention ("tunnelling") onto the perceived source of stress, making a technician more likely to miss an unrelated cue.
Time pressure and heavy workload push technicians toward shortcuts; awareness of this effect is the first defence against it.
Fatigue from poor sleep or shift work degrades judgement as much as alcohol at equivalent levels of impairment, and is worst on night shifts and during a circadian low (roughly 02:00–06:00).
Alcohol, over-the-counter medication and drug use all impair judgement and reaction time — most maintenance organisations mandate a minimum "bottle to throttle" style interval before duty.
⚠ Exam trap: fatigue impairs performance like alcohol, and the fatigued person cannot reliably judge their own impairment — which is why duty-time limits exist.

Solved examples

A technician on their fourth consecutive night shift signs off a task without following the full work card sequence. What is the most likely contributing factor?
Fatigue from circadian disruption on night shift — a fatigued person defaults to habit and skips steps that feel "obviously" complete, even when they are not; fatigue risk management (shift limits, rest periods) exists specifically to control this.

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