Sleep is not voluntary, so if you are drowsy you can fall asleep without knowing it. During a "microsleep" of a few seconds, a car travel 100 yards — plenty of time to place yourself, your passengers and your vehicle in harm's way.
Symptoms of fatigue often include slow reaction times, drifting between lanes, sore or tired eyes, poor concentration, blurred vision, impatience and constant yawning. In many cases, drivers do not remember the last few miles of the trip.
The obvious solution is to get enough sleep the night before trip. But stress, pressure and anxiety fatigue many drivers BEFORE they get behind the wheel. Caffeinated beverages such as coffee and colas are no substitute for sleep. The caffeine may make you feel temporarily alert, but the effects last only a short time.