Fatigue and Drowsiness
Introduction
Fatigue is a major safety problem in many fields, but especially in transportation, because it can cause serious accidents. Fatigue is considered an internal condition for unsafe acts, because it negatively affects the internal state of the human operator. Research has generally focused on pilots, truck drivers, and shift workers.
Fatigue can be a symptom of an illness, but most commonly it is a normal physiological reaction to exertion, lack of sleep, boredom, changes in sleep-wake schedules (including jet lag), or stress.
In some cases, driving after 18 to 24 hours without sleep decreases attention and reaction capacity, as does a blood alcohol content between 0.05 and 0.10%.[2].
Guys
Fatigue can be both physical and mental. Physical fatigue manifests itself in the inability to continue functioning at a normal level; A physically fatigued person cannot lift a box of the same weight that they could lift if they were fresh, nor walk the same distance.[3][4][5].
Mental fatigue, on the other hand, manifests itself in drowsiness or sluggishness. A person with mental fatigue may fall asleep, react very slowly, or not be attentive enough. If the person suffers from microsleeping, they may not realize that, at very short intervals, they fall asleep. Without adequate sleep, certain tasks will seem complicated, concentration will decrease, and ultimately, fatal mistakes can be made.[6].
Factors
The Federal Motor Carrier Safety Administration (FMCSA) identifies 3 main factors in driver fatigue: circadian rhythm, lack of sleep, and cumulative fatigue (industrial or "time-on-task" fatigue).
In addition to the main factors, others have been identified that possibly contribute to driver fatigue. There are the endogenous ones, such as mental stress and the age of the vehicle operator, and the exogenous or environmental ones, such as the presence of cabin pressure higher than sea level during the flight, vehicle noise, and vehicle vibration or acceleration (which contributes to sopite syndrome—motion-induced sleepiness, like that of a baby falling asleep when cradled—). Many exogenous factors are present during actual transportation operations, but not in most laboratory fatigue studies, so an attempt should be made to include them for proper assessment.