Why is night driving more dangerous than daytime driving?

You see hazards later, so you have less time to respond

Roads are more crowded at night

Speed limits are higher at night

Trucks have less traction at night

Your license says you must wear corrective lenses. You forgot them and only need to move the truck a short distance. You should:

Not drive; it is illegal to move the vehicle without them

Drive without them in daylight only

Should you wear dark or tinted glasses at night to cut glare?

No, tinted lenses cut down light you need to see

When are drowsy-driving crashes most likely?

At night, especially after midnight, and in mid-afternoon

Right after a meal at noon only

Getting 6 hours of sleep or less before driving:

Has no effect if you drink coffee

Which is a warning sign of fatigue that should tell you to stop and rest?

Not remembering the last few miles you drove

Wanting to change the radio station

You notice signs of fatigue on the road. The best short-term choice is to:

Stop and take a 15–20 minute nap, or sleep for the night

Drink several energy drinks and keep going

Open the window and push on to your destination

What is true about caffeine and staying alert?

It can help for a few hours but wears off; do not rely on it

It is the only safe cure for drowsiness

When lighting is poor or confusing at night, you should:

Drive slowly enough to stop within the distance you can see

Follow other vehicles closely to use their lights

At night you should be especially alert for drunk drivers:

During rush hour in the morning

At night you must adjust your speed so that:

Your stopping distance is within your sight distance

You stay with the flow of traffic no matter what

You never use more than low beams

You drive at least the speed limit

Why is a clean windshield even more important at night?

Bright lights make dirt on the glass create its own glare

Dirt is harder to see in daylight

Headlights shine through the windshield

To avoid glare from an oncoming vehicle's headlights, you should look:

Slightly to the right, at the right lane or edge marking

Slightly to the left, at the center line

An oncoming driver does not dim his high beams. You should NOT:

Turn on your own high beams to "get back at" him

To see outside better at night, you should set your cab lighting this way:

Interior light off, gauge lights as low as you can still read

Interior light on, gauges bright

Dome light on only when passing

You feel drowsy before a night trip. What should you do?

Take an over-the-counter stimulant

Which group is at increased risk for a fall-asleep crash?

Long-haul commercial drivers and shift workers

Drivers who only drive in mid-morning

Drivers with a passenger who shares driving

Driving at night: vision, glare, fatigue and headlights – CDL General Knowledge study guide

Night driving is more dangerous because you see hazards later. The problems come from three places: the driver, the road, and the vehicle. This lesson covers all three, plus the key numbers for headlights and dimming.

Why night is more dangerous

At night you cannot see hazards as soon as in daylight, so you have less time to respond. A driver who is surprised is less able to avoid a crash. Night problems involve the driver, the roadway, and the vehicle.

Driver factors: vision and glare

Vision. How you use the brake, accelerator and steering depends on what you see. Poor eyesight makes it hard to read traffic and road conditions, spot trouble, and respond in time. Have your eyes checked regularly by an eye specialist; you may not know your vision is poor until it is tested.

If you need glasses or contact lenses to drive: always wear them, even for short trips. If your license lists a corrective lenses restriction, moving a vehicle without them is against the law. Keep a spare pair in the vehicle in case yours break or get lost. Do not use dark or tinted lenses at night, even if you think they help with glare; they cut the light you need to see.

Glare. Bright light can blind you for a short time, and recovery can take several seconds. Even 2 seconds of glare blindness is dangerous: at 55 mph you travel more than half a football field in that time.

Driver factors: fatigue and drowsy driving

Fatigue is physical or mental tiredness caused by strain, repetitive tasks, illness or lack of sleep. Like alcohol and drugs, it hurts your vision and judgment. It causes errors in judging speed and distance, slows how fast you see and react to hazards, hurts critical decisions, and raises crash risk. You could fall asleep at the wheel and kill yourself or others.

Drowsy driving is one of the leading causes of crashes. NHTSA estimates 100,000 police-reported crashes a year come from drowsy driving. The National Sleep Foundation's poll found 60% of Americans have driven while sleepy, and 36% (103 million people) admit they have fallen asleep at the wheel. Some sleep lasts only a few seconds (microsleep), some longer; either way crash risk rises sharply.

When and who. Fall-asleep crashes happen most when sleepiness is strongest: at night (especially after midnight) and in the mid-afternoon, and more so after driving a long time. At higher risk: young males, shift workers, commercial drivers (especially long-haul), and people with untreated sleep disorders or sleep loss. At least 15% of heavy truck crashes involve fatigue. A study of 80 long-haul drivers found they slept less than 5 hours a day. The NTSB found that drowsiness was the likely cause in over half of the crashes in which a truck driver died, and for each truck driver killed, 3 to 4 other people die.

Are you at risk? Before you drive, ask yourself whether you are:

Sleep-deprived or tired: 6 hours of sleep or less triples your risk.
Suffering from insomnia, poor-quality sleep, or a sleep debt.
Driving long distances without proper rest breaks.
Driving through the night, in mid-afternoon, or when you would normally sleep. Many heavy vehicle crashes happen between midnight and 6 a.m.
Taking sedating medicines (antidepressants, cold tablets, antihistamines).
Working more than 60 hours a week (raises risk by 40%), or working more than one job when your main job is shift work.
Driving alone, or on a long, rural, dark or boring road; or after flying and changing time zones.

Preventing drowsiness and spotting the warning signs

Before a trip:

Get enough sleep: adults need 8 to 9 hours to stay alert.
Plan the route: total distance, stopping points and other details.
Schedule trips for hours you are normally awake, not the middle of the night.
Drive with a passenger. Avoid medicines that cause drowsiness.
See your doctor if you have daytime sleepiness, trouble sleeping at night, or take frequent naps. Exercise to give yourself more energy.

While driving: wear sunglasses against glare and eyestrain (in daytime); keep cool with an open window or air conditioning; avoid heavy foods; know your low-energy times of day; take turns driving with another person; take breaks about every 100 miles or 2 hours on long trips; stop and rest or nap when needed.

Caffeine can raise alertness for a few hours, but do not drink too much and do not rely on it; it wears off. Avoid drugs: they may keep you awake for a while, but they do not make you alert.

Warning signs of fatigue (stop and rest): trouble focusing, frequent blinking or heavy eyelids; repeated yawning or rubbing eyes; daydreaming or wandering thoughts; not remembering the last few miles, missing exits or signs; trouble keeping your head up; wandering out of your lane, tailgating, or running onto a shoulder rumble strip; feeling restless and irritable.

Trying to "push on" when tired is much more dangerous than most drivers think and is a major cause of fatal crashes. If you see any sign, stop and sleep for the night or take a 15–20 minute nap. The only safe cure for drowsiness is to get off the road and sleep.

Roadway factors

Poor lighting. Daytime usually has enough light; night does not. Some areas have bright street lights, but many are poorly lit, and on most roads you will rely entirely on your headlights. With less light, you see hazards worse. Road users without lights are hard to see, and many night crashes involve pedestrians, joggers, bicyclists and animals.

Even with lights, the scene can be confusing: signals and hazards blend into a background of signs, store windows and other lights. Slow down when the lighting is weak or confusing, slow enough to stop within the distance you can see.

Drunk drivers. Drivers on alcohol or drugs endanger themselves and you. Be extra alert around bar and tavern closing times. Watch for drivers who cannot stay in their lane or keep a steady speed, who stop for no reason, or show other signs of being under the influence.

Vehicle factors: lights, windshield and mirrors

Headlights are your main light at night, both to see and to be seen. You see much less than in daylight. Low beams let you see about 250 feet ahead; high beams about 350–500 feet. Adjust your speed so your stopping distance stays within your sight distance, meaning slow enough to stop within the range of your headlights.

Dirty headlights may give only half the light they should, which cuts your view and makes you harder to see. Keep them clean and working. Headlights out of adjustment give a poor view and can blind other drivers; have a qualified person adjust them.

Other lights must be clean and working so others can see you: reflectors, marker lights, clearance lights, taillights and identification lights. Turn signals and brake lights matter even more at night to show what you plan to do.

Windshield and mirrors must be clean, more at night than by day. Bright lights make dirt on glass create its own glare, blocking your view (like driving into a rising or setting sun). Clean the windshield inside and outside.

Night driving procedures

Be rested and alert. If you feel drowsy, get sleep first; even a short nap can save lives. Keep eyeglasses clean and unscratched. Do not wear sunglasses at night. Do a complete vehicle inspection, paying attention to all lights and reflectors, and clean the ones you can reach.
Avoid blinding others. Your headlight glare bothers oncoming drivers, and drivers ahead of you through their mirrors. Switch to low beams when an oncoming vehicle is within 500 feet, and when you are 500 feet or less behind another vehicle.
Avoid glare from oncoming vehicles. Do not look straight at their lights. Look slightly to the right, at a right lane line or edge marking if there is one. If other drivers do not dim their lights, do not "get back at them" with your high beams; it adds glare for them and raises crash risk.
Use high beams when you can. Some drivers wrongly use low beams all the time, which badly limits how far they see. Use high beams when it is safe and legal: when you are not within 500 feet of an approaching vehicle (and not close behind one).
Keep the cab dark. A bright cab makes it hard to see outside. Keep the interior light off and set instrument lights as low as you can while still reading the gauges.
Sleepy? Pull off at the closest safe place. Drivers often do not realize how close they are to falling asleep, even as their eyelids close. If it is safe, look at yourself in a mirror. If you look or feel sleepy, stop driving. The only safe cure is sleep.

References and scope

The topic reference is listed below. Sources support verification; the lesson itself is here. The current content needs technical and language review before public launch.

Manual reference: 2.11

Official CDL handbook · Utah ↗States Our editorial approach

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.

Preparing your questions…

Review questions with answers

Why is night driving more dangerous than daytime driving?
1. Roads are more crowded at night
2. You see hazards later, so you have less time to respond
3. Speed limits are higher at night
4. Trucks have less traction at night
Show answer

You see hazards later, so you have less time to respond
At night drivers cannot see hazards as quickly, so they have less time to respond and are less able to avoid crashes.
The problems of night driving involve which three factors?
1. Weather, cargo and fuel
2. Speed, distance and time
3. Signs, signals and lanes
4. The driver, the roadway and the vehicle
Show answer

The driver, the roadway and the vehicle
Night driving problems involve the driver, the roadway, and the vehicle.
Your license says you must wear corrective lenses. You forgot them and only need to move the truck a short distance. You should:
1. Not drive; it is illegal to move the vehicle without them
2. Drive slowly without them
3. Drive without them in daylight only
4. Use sunglasses instead
Show answer

Not drive; it is illegal to move the vehicle without them
If your license requires corrective lenses, it is illegal to move a vehicle without them. Keep a spare pair in the vehicle.
Should you wear dark or tinted glasses at night to cut glare?
1. Yes, always at night
2. Yes, but only on highways
3. No, tinted lenses cut down light you need to see
4. Only when it is raining
Show answer

No, tinted lenses cut down light you need to see
Avoid dark or tinted lenses at night. They reduce the light you need under night conditions.
Even 2 seconds of glare blindness is dangerous. At 55 mph, in that time you travel about:
1. 10 feet
2. More than half a football field
3. A quarter mile
4. The length of your truck
Show answer

More than half a football field
A vehicle at 55 mph travels more than half a football field in 2 seconds.
Fatigue affects your driving in a way similar to:
1. Drinking coffee
2. Listening to music
3. Using cruise control
4. Alcohol and drugs
Show answer

Alcohol and drugs
Like alcohol and drugs, fatigue impairs your vision and judgment.
NHTSA estimates about how many police-reported crashes a year result from drowsy driving?
1. 100,000
2. 10,000
3. 1,000
4. 1 million
Show answer

100,000
NHTSA estimates 100,000 police-reported crashes each year are the result of drowsy driving.
When are drowsy-driving crashes most likely?
1. Mid-morning only
2. Right after a meal at noon only
3. At night, especially after midnight, and in mid-afternoon
4. Only on weekends
Show answer

At night, especially after midnight, and in mid-afternoon
Crashes tend to happen when sleepiness is strongest: at night (especially after midnight) and in the mid-afternoon.
At least what percent of all heavy truck crashes involve fatigue?
1. 5%
2. 15%
3. 50%
4. 60%
Show answer

15%
At least 15% of all heavy truck crashes involve fatigue.
Getting 6 hours of sleep or less before driving:
1. Has no effect if you drink coffee
2. Doubles your risk
3. Lowers your risk at night
4. Triples your risk
Show answer

Triples your risk
Being sleep-deprived (6 hours or less) triples your crash risk.
Working more than 60 hours a week increases your fatigue crash risk by about:
1. 40%
2. 10%
3. 100%
4. 5%
Show answer

40%
Working over 60 hours in a week raises your crash risk by about 40%.
How much sleep do adults need to maintain alertness?
1. 4 to 5 hours
2. 5 to 6 hours
3. 8 to 9 hours
4. 11 to 12 hours
Show answer

8 to 9 hours
Adults need 8 to 9 hours of sleep to stay alert.
On long trips, about how often should you take a break?
1. Every 50 miles or 30 minutes
2. Every 100 miles or 2 hours
3. Every 300 miles or 6 hours
4. Only when you need fuel
Show answer

Every 100 miles or 2 hours
On long trips, stop for a break roughly every 2 hours or 100 miles.
Which is a warning sign of fatigue that should tell you to stop and rest?
1. Feeling hungry
2. Wanting to change the radio station
3. Seeing a rest area sign
4. Not remembering the last few miles you drove
Show answer

Not remembering the last few miles you drove
Warning signs include trouble remembering the last few miles, missing exits, heavy eyelids, yawning, drifting and hitting rumble strips.
You notice signs of fatigue on the road. The best short-term choice is to:
1. Stop and take a 15–20 minute nap, or sleep for the night
2. Drink several energy drinks and keep going
3. Open the window and push on to your destination
4. Drive faster to arrive sooner
Show answer

Stop and take a 15–20 minute nap, or sleep for the night
If you notice fatigue, stop and sleep for the night or take a 15 to 20 minute nap. "Pushing on" is a major cause of fatal crashes.
What is true about caffeine and staying alert?
1. It cures fatigue completely
2. It works better than sleep
3. It can help for a few hours but wears off; do not rely on it
4. It is the only safe cure for drowsiness
Show answer

It can help for a few hours but wears off; do not rely on it
Caffeine can raise awareness for a few hours, but it wears off. Do not rely on it. The only safe cure is sleep.
When lighting is poor or confusing at night, you should:
1. Use your high beams in town
2. Drive slowly enough to stop within the distance you can see
3. Follow other vehicles closely to use their lights
4. Keep your normal daytime speed
Show answer

Drive slowly enough to stop within the distance you can see
Drive slower when lighting is poor or confusing, slow enough to stop in the distance you can see ahead.
At night you should be especially alert for drunk drivers:
1. Around school opening times
2. At sunrise
3. During rush hour in the morning
4. Around bar and tavern closing times
Show answer

Around bar and tavern closing times
Be especially alert around closing times for bars and taverns.
With low beams, about how far ahead can you see?
1. 250 feet
2. 100 feet
3. 500 feet
4. 1,000 feet
Show answer

250 feet
Low beams let you see about 250 feet ahead; high beams about 350–500 feet.
High beams let you see about how far ahead?
1. 150–200 feet
2. 200–250 feet
3. 350–500 feet
4. 800–1,000 feet
Show answer

350–500 feet
With high beams you can see about 350–500 feet.
At night you must adjust your speed so that:
1. You stay with the flow of traffic no matter what
2. Your stopping distance is within your sight distance
3. You never use more than low beams
4. You drive at least the speed limit
Show answer

Your stopping distance is within your sight distance
Go slowly enough to stop within the range of your headlights; otherwise you will not have time to stop when you see a hazard.
Dirty headlights may give only about how much of the light they should?
1. 90%
2. 75%
3. 10%
4. Half
Show answer

Half
Dirty headlights may give only half the light they should, so you see less and others see you less.
Why is a clean windshield even more important at night?
1. Bright lights make dirt on the glass create its own glare
2. Dirt is harder to see in daylight
3. Wipers do not work at night
4. Headlights shine through the windshield
Show answer

Bright lights make dirt on the glass create its own glare
Bright lights at night can make dirt on the windshield or mirrors create glare, blocking your view. Clean the inside and outside.
You must dim your headlights when an oncoming vehicle is within:
1. 200 feet
2. 1,000 feet
3. 500 feet
4. 100 feet
Show answer

500 feet
Switch to low beams when an oncoming vehicle is within 500 feet, and when you are 500 feet or less behind another vehicle.
To avoid glare from an oncoming vehicle's headlights, you should look:
1. Directly at the headlights
2. Slightly to the right, at the right lane or edge marking
3. At your mirrors
4. Slightly to the left, at the center line
Show answer

Slightly to the right, at the right lane or edge marking
Do not look straight at oncoming lights. Look slightly right at a right lane or edge marking.
An oncoming driver does not dim his high beams. You should NOT:
1. Turn on your own high beams to "get back at" him
2. Look slightly to the right
3. Slow down if needed
4. Keep your low beams on
Show answer

Turn on your own high beams to "get back at" him
Do not flash or turn on your high beams in return; it increases glare and the chance of a crash.
At night, the safest habit is to keep your low beams on at all times. True or False?
1. True
2. False
Show answer

False
False. Use high beams when it is safe and legal (no vehicle within 500 feet). Always using low beams cuts down how far you can see.
To see outside better at night, you should set your cab lighting this way:
1. Interior light on, gauges bright
2. Interior light on, gauges off
3. Dome light on only when passing
4. Interior light off, gauge lights as low as you can still read
Show answer

Interior light off, gauge lights as low as you can still read
A bright cab makes it harder to see outside. Turn the dome light off and set the gauge lights as low as you can while still reading them.
You feel drowsy before a night trip. What should you do?
1. Drink coffee and leave on time
2. Drive with the window open
3. Sleep before you drive
4. Take an over-the-counter stimulant
Show answer

Sleep before you drive
When you feel drowsy, get sleep before the trip. Even a short nap can save lives; sleep is the only safe cure.
Which group is at increased risk for a fall-asleep crash?
1. Long-haul commercial drivers and shift workers
2. Drivers who sleep 8 to 9 hours
3. Drivers who only drive in mid-morning
4. Drivers with a passenger who shares driving
Show answer

Long-haul commercial drivers and shift workers
Young males, shift workers, commercial (especially long-haul) drivers, and people with sleep disorders or sleep loss are at higher risk.
For others to see you at night, which of these must be clean and working?
1. Only the headlights
2. Only the interior dome light
3. Only the horn and mirrors
4. Reflectors, marker, clearance, tail and identification lights
Show answer

Reflectors, marker, clearance, tail and identification lights
Reflectors, marker lights, clearance lights, taillights and identification lights must be clean and working so you are seen easily.
Many heavy-vehicle crashes linked to drowsiness happen during which hours?
1. 6 a.m. to noon
2. Noon to 3 p.m.
3. Midnight to 6 a.m.
4. 6 p.m. to 9 p.m.
Show answer

Midnight to 6 a.m.
Many heavy motor vehicle crashes happen between midnight and 6 a.m., when the body expects to be asleep.
Which of these raises your risk of a fall-asleep crash?
1. Sleeping 8 to 9 hours before a trip
2. Driving with a passenger who shares the driving
3. Scheduling the trip for your normal waking hours
4. Taking an antihistamine or cold tablet
Show answer

Taking an antihistamine or cold tablet
Sedating medicines such as antidepressants, cold tablets and antihistamines increase the risk of drowsy driving.