Fatigue Driving

Because fatigue affects the same functions that make driving safe: reaction time slows, attention narrows, judgment of speed and distance becomes less accurate, and the driver is less aware of how impaired they are. At highway speeds, even a brief lapse — a second or two of reduced awareness or a micro-sleep — covers a significant distance. Fatigue-related incidents tend to be severe because a driver who has fallen asleep or lost attention doesn't brake or steer before impact.

The signs that you need to stop:

• Difficulty keeping eyes open or repeatedly blinking to clear blurry vision

• Yawning frequently

• The vehicle drifting out of lane or toward rumble strips

• Missing exits or road signs you would normally notice

• Difficulty remembering the last few miles driven

• Feeling irritable or having difficulty concentrating on the road

Caffeine can temporarily reduce the feeling of sleepiness and provide a short window of improved alertness, but it doesn't restore reaction time or judgment to the level of a rested driver. It also takes time to take effect. The only reliable solution to driving fatigue is rest. If you feel the need for caffeine to continue driving, treat it as a signal that a rest stop is needed — use the short alertness window it provides to find a safe place to stop, not to push through to the destination.

Late night to early morning and early-to-mid afternoon tend to be the periods when the body's natural alertness drops most. This is partly circadian — the body has biological low points at these times regardless of how much sleep the driver had. Long journeys that start in the early afternoon can arrive at this natural low point during the most demanding hours of driving, particularly if the driver is already sleep-deprived.

Build in planned stops before you feel tired, not after. On a long journey, stopping for a short rest every couple of hours is more effective at maintaining alertness than driving until fatigue forces a stop. If possible, avoid driving during your body's natural low-alertness periods. Share driving if you have a co-driver. Allow enough total journey time that a stop doesn't feel like it's threatening the schedule — time pressure and fatigue together are a particularly risky combination.

These measures reduce the feeling of discomfort that accompanies fatigue but don't restore the cognitive functions that matter for safe driving. A driver who is cold and uncomfortable but staying awake through discomfort has not solved the underlying fatigue — they've just masked it temporarily. Reaction time, lane-keeping accuracy, and decision-making remain impaired. These approaches buy a few minutes at most; the right response to driving fatigue is always to stop and rest.