The risks, dangers, and often tragic results of drowsy driving are alarming. The National Highway Traffic Safety Administration (NHTSA) estimates that at least 100,000 police-reported crashes annually are the direct result of driver fatigue. That means an average of 1,550 deaths, 71,000 injuries and $12.5 billion in monetary damages each year because of fatigue-related accidents.
With the upcoming end of Daylight Saving Time and the occasion of the National Sleep Foundation’s (NSF) Drowsy Driving Prevention Week, to be held November 6-13, now is a good time to review the factors that influence the likelihood of driver fatigue and the performance implications of drowsy driving for professional drivers.
The Risk of Fatigue
While nobody is immune to the effects of fatigue, commercial drivers are at a significantly higher risk for fall-asleep crashes because they are generally required to drive long distances for long periods of time, often at night, and they frequently work irregular schedules.
The Federal Motor Carrier Safety Administration (FMCSA) has attempted to address the problem through Hours of Service (HOS) regulations, but compliance with the HOS limits in no way means that a driver will be well rested. There are a number of factors that influence the likelihood that a driver will become fatigued, including:
• The number of hours a driver has been awake before driving. The ability Be Alert to Drowsy Driving to function properly begins to drop at the 13th hour of being awake, and continues to decline as the hours progress.
• The quantity and quality of the driver’s last sleep period.
• The time of day. Our bodies and brains operate on an internal body clock (circadian rhythm) that regulates the approximately 24-hour cycle of biological processes and influences how alert or drowsy we are at certain times of the day.
• The level of physical activity or mental or cognitive work. Extended periods of driving alone, for example, can make it difficult to maintain alertness and vigilance.
• The presence of untreated sleep disorders. Conditions such as obstructive sleep apnea (OSA), insomnia, narcolepsy, upper airway obstruction, restless leg syndrome, and periodic limb movements can seriously disrupt sleep.
• Alcohol consumption or the use of sedative drugs.
Most adults feel rested and perform best with seven to nine hours of uninterrupted sleep. Failure to get sufficient sleep can lead to a build-up of sleep debt. Until this debt is repaid by sleeping, drivers will have a greater risk of having a fatigue-related accident.
Performance Implications
Fatigue is a general term commonly used to describe the experience of being “sleepy,” “tired,” “drowsy,” or “exhausted.” Key warning signs of fatigue include, but are not limited to:
• Increased desire to sleep;
• Frequent yawning;
• Head nodding and/or head shaking to stay awake;
• Sore or heavy eyes or impaired vision, such as slowed speed of eye movement (staring), increased difficulty to visually focus or keep eyes open;
• Slowed reaction times;
• Loss of concentration and attention (i.e., daydreaming);
• Impaired judgment and problems with processing information;
• Rapid loss of short-term memory capability;
• Loss of motivation;
• Increased moodiness, irritability or aggressive behavior;
• Microsleeps (brief episodes of “nodding off,” marked by a blank stare, head snapping, prolonged closing of the eyes, and/or an attention loss of 5-20 seconds).
When behind the wheel, fatigue can greatly impair a person’s ability to drive and maneuver safely, and may be demonstrated by:
• Failure to respond to road sign instructions, road changes and the actions of other vehicles;
• Random variations in speed;
• Erratic shifting;
• Inappropriate braking for conditions;
• Lane deviations and/or hitting rumble strips on the road;
• Tendency to follow other vehicles too closely;
• Failure to remember the last several miles of driving.
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