Federal rules do not allow you to operate a commercial motor vehicle when illness, fatigue or another cause, such as a medication's side effects, has left you unable to drive safely. A vague worry about getting sick is not enough, and taking medicine is not automatically prohibited.
Fatigue is the body's need for rest, and only sleep meets that need. Stimulant drugs and coffee may hide tiredness for a short time without removing it, and even a half-hour nap does more good than a half-hour coffee break.
With nobody else aboard, there is no one to talk to or to notice that you are getting drowsy, so a solo driver can tire more easily. Plenty of sleep and regular stops lower the risk of fatigue rather than raise it.
Alcohol acts first on the parts of the brain that govern judgment and self-control, so these slip as BAC goes up, and drinkers often fail to notice their own impairment. Nothing about a higher BAC speeds up sobering; only time brings it back down.
Chatting with riders splits the driver's attention, adding a distraction on top of fatigue. A drowsy driver should instead stop in a safe place and get some rest.
Anything that takes your eyes, hands or mind off driving is a distraction, and that includes conversations with passengers and fiddling with the radio. Eating, drinking, smoking and reading maps are other common examples.
A depressant slows the central nervous system, so alcohol dulls judgment, delays reactions and brings on drowsiness, all while making drivers feel more capable than they really are.
Only rest truly cures sleepiness, so leave the road and take a nap or a break before going on. Coffee and other stimulants help only briefly and can leave you more tired when they wear off, and driving slower does nothing to make you more alert.
Feeling better does not mean the medicine has stopped causing drowsiness; as long as you keep taking it, it can still slow your reactions and dull your alertness. A passenger or a pressing reason to travel does not remove that risk.
Standard servings of beer, wine and liquor contain about the same amount of alcohol, so what counts is how much you drink, not which drink you choose. Coffee and fresh air cannot speed up sobering, and alcohol affects everyone who drinks.
Many drugs, even ones a doctor prescribes, can dull alertness, coordination or judgment, which raises the risk of a crash and of being arrested. Pep pills and other stimulants only hide fatigue for a while and can leave a driver even more tired when they wear off.
Regular stops, roughly every two hours or 100 miles, give you a chance to get out, walk around, and rest before drowsiness builds up. Caffeine and cold showers only cover up tiredness for a short time.
Drugs, including some legal prescription and over-the-counter medicines, can slow reactions and cloud judgment, which leads to crashes, and driving while impaired by them can get you arrested. A prescription alone does not mean a drug is safe to use behind the wheel.
Fatigue goes away only with rest, so build regular short stops into your trip and take them before sleepiness hits. Many cold remedies cause drowsiness, and driving during the hours you would normally be asleep makes fatigue much more likely.
Multiply the serving size by the strength: 12 ounces at 5% and 5 ounces at 12% both come to 0.6 ounce of pure alcohol. Each counts as one standard drink, the same as a 1.5-ounce shot of 40% liquor.
Sleep is the only real cure for drowsiness; caffeine and sugar may hide it for a short time, but they do not make you alert. If you are sleepy, rest before the trip, since even a short nap can make a big difference.
Anything that draws your eyes, hands or mind from the road is a distraction, including conversations with passengers and fiddling with the radio, as well as eating, drinking, reading maps or reaching for something that fell.
Feeling sleepy is the cue to get off the road, however many hours you have driven and however near the end of the trip you are. Fatigue can set in long before any legal driving limit, and only rest or sleep relieves it.
The body gets rid of alcohol at a steady rate of roughly one drink per hour, so four drinks need about four hours. Coffee, fresh air or a cold shower cannot speed this up; only time sobers a person.
Alcohol and other drugs can strengthen each other, so together they can impair a driver far more than either one would alone. This can happen even when the driver's BAC is below the legal limit.
Many cold and allergy remedies contain antihistamines or alcohol, which can cause drowsiness and slow your reactions. Being sold over the counter does not make a medicine safe to take before driving, and the time of day does not change its side effects.
Every question in this set has its own page with the correct answer and an explanation.
