CDL Practice Test Online — Free Permit Test Prep

1. What should you do when merging?

• A. Merge at a much lower speed than the flow of traffic.
• B. Check your mirrors to be sure the gap in traffic is big enough to enter safely.
• C. Pull into the gap first, then check your mirrors to see if it was large enough.

Correct answer: B

Explanation: Your truck accelerates slowly and needs much more room than a car, so you must enter traffic through a larger gap. Your mirrors show the vehicles beside and behind you, so check them before you merge and pick a gap you can enter safely. Pull into a gap that is too small and the drivers behind you must brake hard, which can cause a crash. Signal first so other drivers know what you plan to do. Merge at the speed of the traffic; entering much slower than the flow forces everyone behind you to slow down.

2. Where must you keep hazardous materials shipping papers while you are driving?

• A. Attached to the sun visor
• B. In the glove box with the other papers
• C. In a pouch on the driver's door

Correct answer: C

Explanation: After a crash you may be injured and unable to speak. Firefighters and police must still learn what you are hauling, so the papers have to be where they can grab them at once. The door pouch does that: it is in reach while you drive and easy to see from the open door. When you leave the cab, the papers go in the door pouch or on the driver's seat, and the emergency response information stays with them. A sun visor clip or the glove box hides the papers when seconds matter.

3. Which of these statements about driving through a tunnel is correct?

• A. There may be strong winds when exiting.
• B. The wind at the exit is worse for heavy trucks than light ones.
• C. Driving beside another vehicle is safest as you leave a tunnel.

Correct answer: A

Explanation: Inside a tunnel the walls block the wind. At the exit that shelter ends, so a gust can hit you all at once. Strong wind makes it difficult to stay in your lane, and the problem is worse for lighter vehicles. An empty trailer can be pushed toward the next lane. Keep a firm grip on the wheel, slow down, and do not drive alongside other vehicles as you come out.

4. Which of these vehicles off-tracks the most when it turns?

• A. Tractor with a 45-foot trailer
• B. 28-foot box truck
• C. 45-foot straight truck

Correct answer: A

Explanation: Off-tracking happens when the rear wheels take a different path from the front wheels in a turn. The longer the vehicle, the more it off-tracks. The tractor with a 45-foot trailer has the greatest overall length of the three choices. Also, the trailer's rear wheels off-track more than the rear wheels of the tractor. In a turn, this wide swing can make a large vehicle strike other vehicles or objects. Turn slowly and give the trailer room. The 45-foot straight truck pulls no trailer and is shorter overall, so it off-tracks less.

5. When should you sound your horn?

• A. To warn the drivers behind you that you are slowing down
• B. To tell another driver that it is safe to pass you
• C. If it helps to avoid a crash

Correct answer: C

Explanation: Your horn is a warning device, not a message. Use it when the sound can prevent a crash, to alert a driver, walker, or cyclist who has not seen you. When you pass someone, tap the horn lightly if the law allows. A blast you do not need can startle people and push them into the very move you feared, so it creates danger instead of preventing it. Your brake lights, not your horn, warn the drivers behind you that you are slowing. Never use the horn to tell another driver that it is safe to pass you. Even after you sound the horn, keep driving so you can avoid a crash if the other person never hears you.

6. Which statement about alcohol is NOT true?

• A. A drinker can control how fast his or her body gets rid of alcohol.
• B. Alcohol passes straight into the blood, which takes it to the brain.
• C. BAC is determined by how much you drink, how fast you drink, and your weight.

Correct answer: A

Explanation: Your body handles alcohol at a fixed speed. The liver processes only about one-third of an ounce of alcohol per hour, and nothing speeds it up. Only time lowers your blood alcohol; coffee and a cold shower do not. So a drinker cannot control how fast the body takes in or gets rid of alcohol, which makes that statement the false one. Drink faster than the liver can work and alcohol builds up in your blood, impairing judgment, vision, coordination and reaction time before you feel drunk. BAC does depend on how much you drink, how fast you drink, and your weight.

7. If ____ or more of the leaves in any leaf spring are missing, your vehicle is put out of service and cannot be driven.

• A. 1/4
• B. 1/2
• C. 1/3

Correct answer: A

Explanation: Leaf springs hold up the vehicle and its load and keep the axle in place. When leaves are missing, the spring can collapse. The frame or body can then drop onto a tire, and you can lose control or roll the vehicle over. That is why the limit is strict: if 1/4 or more of the leaves in any leaf spring are missing, the vehicle is put out of service and stays parked until it is repaired. Do not read the limit as 1/2. One-fourth is already enough, and any broken or missing leaf is dangerous.

8. Which statement about transporting hazardous materials is correct?

• A. Only materials labeled as explosives or poisons pose a risk to health and safety.
• B. Any truck carrying any amount of hazardous materials must have placards.
• C. All hazardous materials pose a risk to health, safety, and property.

Correct answer: C

Explanation: Risk is built into the definition of hazardous materials: they are products that threaten health, safety, and property in transport. So the risk applies to every hazard class, not only explosives or poisons. Many hazardous products can injure or kill a person who touches them. For this reason, the shipper packages, marks, and labels them, and you refuse any leaking package instead of hauling it. Placards do not show whether a load is dangerous. The rules require placards only for certain types or quantities. A truck without placards may still carry hazardous materials.

9. Which of these affects a person's blood alcohol concentration (BAC)?

• A. Their height
• B. Their weight
• C. The time of day they drink

Correct answer: B

Explanation: Alcohol spreads through the blood in your body. A heavier person carries more blood, so the same drink is more diluted. A lighter person reaches a higher BAC from the same drinks. Three things set your BAC: how much you drink, how fast you drink, and your weight. Height is not one of them. The time of day does not matter. How fast you drink does, because the liver handles only about one drink per hour. The extra alcohol builds up in your blood. Driving a CMV at .04% BAC or higher is illegal, and a lower BAC still hurts your judgment, vision, and reaction time.

10. What is the right way to hold a steering wheel?

• A. With both hands, on opposite sides of the wheel
• B. With one hand on the top of the wheel and the other on your lap
• C. With both hands close together at the top of the wheel

Correct answer: A

Explanation: A firm grip with both hands keeps you in control when the road jolts the wheel. Hit a curb or a pothole with a loose or one-handed hold, and the wheel can pull away from you. A front tire that fails can twist the wheel out of your hands the same way. Hands on opposite sides also let you turn fast in an emergency without moving your grip first, so keep them there all the time, not just when trouble starts. One hand on top and the other on your lap leaves nothing to resist that sudden pull.

11. Which statement about drug use is correct?

• A. Taking drugs is safe if driving short distances.
• B. Use of drugs can lead to an accident, arrest, or both.
• C. Over-the-counter cold medicine is always safe to take before driving.

Correct answer: B

Explanation: Drugs make you less alert and reduce your ability to drive safely. The law bans driving under the influence of any controlled substance, amphetamine, or narcotic. It also bans any other substance that makes a driver unsafe, including cold medicines that make you drowsy. Drug use leads to traffic accidents that cause death, injury, and property damage. It also leads to arrest, fines, jail sentences, and the end of your driving career. A short trip is not safer, because the drug still affects your judgment and reaction time. Never mix drugs with driving.

12. When may a driver without a hazardous materials endorsement drive a vehicle that carries hazardous materials?

• A. The driver holds a commercial learner's permit.
• B. The vehicle does not require placards.
• C. The hazardous materials are in a sealed, unbreakable container.

Correct answer: B

Explanation: Placards are the diamond-shaped warning signs that tell other drivers and emergency crews what the load can do. The endorsement exists so the driver of a placarded load knows how to load, mark and haul it safely. The rule therefore turns on placards, not on packaging. If the material's type and quantity require placards, you need the hazardous materials endorsement. If no placards are required, you may drive the vehicle without one. A sealed container does not remove a placard requirement, and a learner's permit does not replace the endorsement. Driving a placarded load without the endorsement is a serious violation and leaves responders guessing at a crash.

13. What would be your total stopping distance at 55 mph on dry pavement?

• A. About half the length of a football field
• B. The length of a basketball court
• C. More than the length of a football field

Correct answer: C

Explanation: At 55 mph on dry pavement, your vehicle needs a minimum of 419 feet to stop. Three parts add up to that number: 142 feet while your brain recognizes the hazard, 61 feet while your foot reaches the brake, and 216 feet of braking. A football field is the closest picture of that much space, so hold that much room ahead of you. Leave less, and you are still braking when you reach the hazard. Half a football field or a basketball court is far too short: you cover that much road before the brakes even take hold.

14. You see a hazard ahead that will make you slow down. How do you warn the drivers behind you?

• A. Use your four-way flashers or brake lights to warn others.
• B. Wave the drivers behind you past when the lane looks clear.
• C. Turn on your high beam headlights to signal danger.

Correct answer: A

Explanation: Your vehicle is big, so the drivers behind you cannot see the hazard you see. They do not expect you to slow down. Tap the brake pedal a few times. The flashing brake lights warn them early, while they still have room to stop. Turn on your four-way emergency flashers when you are already driving very slowly or are stopped. Without that warning, a following driver closes on you fast and hits you from behind. High beams do not help here. They shine forward, away from the drivers who need the warning, and they bother other drivers day or night.

15. What is the safest method to merge onto the road?

• A. Use your horn to alert others before merging.
• B. Wait for a gap in traffic large enough to enter the road safely.
• C. Pull out slowly and let the traffic behind you slow down.

Correct answer: B

Explanation: A loaded commercial vehicle accelerates slowly and takes up a lot of road. You need a much larger gap than a car needs. Check your mirrors and judge the gap before you move. Enter only when the gap lets you reach traffic speed without forcing anyone to brake. A heavier load needs an even bigger gap. Pull into a small gap and the traffic behind you must brake hard; a rear-end crash or a sideswipe can follow. A horn does not create space. Never assume other drivers will slow down to let you in.

16. Which statement about loading cargo is correct?

• A. Cargo does not need to be secured if it's under 100 pounds.
• B. Heavy cargo should be loaded on top of lighter cargo.
• C. State law sets the legal weight limits.

Correct answer: C

Explanation: States set the legal weight limits you must stay within. Each state has maximums for gross vehicle weight rating, gross combination weight rating, and axle weight. Axle limits often come from a bridge formula. It allows less weight when axles sit closer together, so heavy loads do not overload bridges and roads. Overloading hurts steering, braking, and speed control. Stopping distance grows, and brakes can fail when they work too hard. Securement is a separate rule: blocking and bracing keep cargo from sliding, whatever it weighs.

17. You start moving from a stop and the drive wheels begin to spin. What should you do?

• A. Press the brake pedal firmly.
• B. Increase the engine's speed.
• C. Take your foot off the accelerator.

Correct answer: C

Explanation: When drive wheels spin, the tires have lost their grip. Pressing the accelerator keeps sending power to those wheels. Take your foot off, and the power stops, so the tires can grip the road again. If you keep the power on, the spin turns into a drive-wheel skid. The back of the vehicle may slide sideways, or a trailer may jackknife. More engine speed seems like a way out, but it only makes the wheels spin faster. On wet or snowy roads with poor traction, add speed slowly and gently.

18. What should you do when a heavy load slows you down as you climb a hill?

• A. Increase your speed significantly.
• B. Turn on your hazard lights and stop.
• C. Shift to a lower gear.

Correct answer: C

Explanation: Gravity works against you on every upgrade, and a heavy load makes that pull stronger. A lower gear sends more pulling force to the drive wheels, so the truck keeps climbing instead of losing speed. The steeper the grade, the longer the grade, and the heavier the load, the lower the gear you need. Stay in too high a gear and the engine struggles, the truck slows further, and you can stall or roll back into the traffic behind you. Speeding up cannot fix this. The weight and the grade, not the throttle, are holding you back.

19. How should you arrange reflective triangles when parking on the roadside of a straight, level, four-lane divided highway?

• A. One within 10 feet of the front of the vehicle, one about 50 feet to the rear, and one about 250 feet to the rear
• B. One within 10 feet of the rear of the vehicle, one about 100 feet to the rear, and one about 100 feet to the front
• C. One within 10 feet of the rear of the vehicle, one about 100 feet to the rear, and one about 200 feet to the rear

Correct answer: C

Explanation: On a divided highway, traffic reaches you only from behind. You place all three devices toward that approaching traffic. Put one within 10 feet of the rear of the vehicle to mark where it sits. Put the second about 100 feet back and the third about 200 feet back. That spacing gives an approaching driver time to see you and change lanes. Put the devices out within ten minutes of stopping. Drivers have crashed into the rear of parked trucks because they thought the vehicle was still moving. A triangle placed in front of the vehicle warns nobody on this road.

20. Which statement about inspecting your wheels and rims before a trip is true?

• A. A wheel is safe to drive with one lug nut missing if the rest are tight.
• B. Rust around wheel nuts may mean that they are loose.
• C. A cracked rim is safe to use once the crack has been welded.

Correct answer: B

Explanation: Wheel nuts that begin to loosen let the wheel shift slightly on the hub. That movement wears the metal and leaves rust streaks running out from the nuts. Rust there is a warning sign, so check the nuts for tightness before you drive. After any tire change, stop a short while later and check tightness again. A wheel that works loose can leave the axle at speed and cause a crash. A cracked rim is never safe, even though the wheel still turns, because the crack can let the tire come off the rim.