CDL Practice Test
This is a free 15-question sampler across the CDL knowledge tests, written by the StudyPDF team. It mixes general knowledge, the headline air brake facts, combination vehicle basics and the rules and paperwork every applicant is asked about, using multiple choice, select all that apply and fill in the blank. Answer all 15 questions, then check your score and read the explanation for every question. Your own state's CDL manual is still the book your real test comes from, so keep it next to you.
The CDL skills test is made up of which three parts?
All Work & Citizenship quizzes
- Practice test · 15 questions
CDL General Knowledge Practice Test
- Practice test · 15 questions
CDL Air Brakes Practice Test
- Practice test · 15 questions
CDL Combination Vehicles Practice Test
Now make your own
Upload your prep book, slides or notes, or just tell Bo what you want to learn. You do not need a document to start.
All 15 questions at a glance
Prefer to read before you play? Every question in the sampler is listed below. Answers and explanations stay collapsed until you open them.
1. The CDL skills test is made up of which three parts?
- A. A written test, a vision test and a road test
- B. A vehicle inspection test, a written test and a drug test
- C. A vehicle inspection test, a basic vehicle control test and an on-road driving test
- D. A basic control test, a coupling test and an air brake test
Show answer and explanation
Answer: C. A vehicle inspection test, a basic vehicle control test and an on-road driving test
The knowledge tests are taken on a computer or on paper, and the skills test is the practical part in the vehicle. It always runs in the same order: you show the examiner your pre-trip inspection, then you demonstrate basic control such as backing and offset alley docking, then you drive on public roads. You have to pass all three, and you take the skills test in a vehicle that matches the class of license you want.
2. You have to stop on the shoulder of a divided highway. Where do the three warning devices go?
- A. All three together, about 50 feet behind the vehicle
- B. One about 10 feet behind the vehicle, one about 100 feet behind and one about 200 feet behind
- C. One 10 feet in front of the vehicle, one 100 feet behind and one 500 feet behind
- D. One at each corner of the vehicle and one on the roof
Show answer and explanation
Answer: B. One about 10 feet behind the vehicle, one about 100 feet behind and one about 200 feet behind
On a divided or one way road the devices go behind you, toward the traffic that is coming: about 10 feet back on the traffic side, about 100 feet back and about 200 feet back. On a two lane two way road you protect both directions instead, with a device about 100 feet ahead and about 100 feet behind. You have 10 minutes to get them out, and on a hill or a curve you move the far one back so drivers see it before they see you.
3. You are driving a 50 foot combination at 55 mph on a dry road. Using the rule of thumb in the CDL manual, what is your minimum following distance?
- A. 3 seconds
- B. 4 seconds
- C. 5 seconds
- D. 6 seconds
Show answer and explanation
Answer: D. 6 seconds
The rule is one second for every 10 feet of vehicle length at speeds below 40 mph, then add one more second above 40 mph. Fifty feet gives you five seconds, and the extra second for speed makes six. Count the seconds between the vehicle ahead passing a fixed object and your own front bumper reaching it, and add more time on wet or icy roads and at night.
4. You have loaded and secured your cargo and started the trip. When must you first re-check the securement?
- A. There is no need to check again once it is secured
- B. Within the first 50 miles
- C. After the first 150 miles
- D. Only at the end of the driving day
Show answer and explanation
Answer: B. Within the first 50 miles
You inspect the cargo and its securement within the first 50 miles, because tiedowns settle and loosen once the load starts moving. After that you re-check every 3 hours or 150 miles, or each time you take a break, whichever comes first. The driver is responsible for the load even when somebody else loaded and secured it, so a sealed trailer you cannot inspect does not remove your duty to stay within weight limits.
5. Which of the following are correct ways to control your speed on a long, steep downgrade?
Select all that apply.
- A. Select a low gear before you start down the grade
- B. Shift into neutral and coast to save fuel
- C. Use the braking effect of the engine as your main way of holding speed
- D. Apply the brakes firmly to slow about 5 mph below your safe speed, then release them
- E. Hold light, steady pressure on the brakes all the way down
- F. Wait until you feel the brakes fading before you downshift
Show answer and explanation
Answer: A. Select a low gear before you start down the grade, C. Use the braking effect of the engine as your main way of holding speed, D. Apply the brakes firmly to slow about 5 mph below your safe speed, then release them
Gravity is what speeds you up, so the plan has to be set before you start down. Pick the gear at the top, because a heavy vehicle may not go back into gear once it is rolling fast. Let the engine hold most of the speed and use the brakes in firm, short applications, known as snub braking, so they get time to cool between them. Riding the brakes cooks the linings until they stop working, and coasting in neutral is both unsafe and illegal in most states.
6. Complete the sentence.
Under the federal hours of service rules, a property carrying driver may drive for up to _____ hours, and only after _____ consecutive hours off duty.
Options for blank 1: 8, 10, 11, 14
Options for blank 2: 8, 10, 11, 12
Show answer and explanation
Answer: 11, 10
Those 11 driving hours have to fit inside a 14 hour window that starts when you come on duty, and the window does not stop for meals or loading. You also need a 30 minute break after 8 cumulative hours of driving, and you are capped at 60 hours in 7 days or 70 hours in 8 days depending on your carrier's schedule. Passenger carrying drivers work to different numbers, and some short haul drivers qualify for an exception, so read the rule that matches your job.
7. You pass your CDL skills test in a vehicle that does not have air brakes. What does that mean for your licence?
- A. Nothing, because the air brakes knowledge test on its own covers you
- B. You may drive air brake vehicles for one year and then have to retest
- C. Your CDL carries an air brake restriction and you may not drive a commercial vehicle with air brakes
- D. You may drive air brake vehicles as long as a licensed driver rides with you
Show answer and explanation
Answer: C. Your CDL carries an air brake restriction and you may not drive a commercial vehicle with air brakes
The restriction, usually printed as an L, lands on your licence if you fail the air brakes knowledge test, skip the air brake part of the pre-trip inspection, or take the skills test in a vehicle without air brakes. Most vehicles you will be hired to drive have them, so it closes off a lot of work. Getting it removed means going back and passing the air brake portions in a vehicle that actually has air brakes.
8. Air pressure is falling and the warning has come on. Why should you not pump or fan the brake pedal?
- A. Pumping overheats the brake drums
- B. Pumping locks the trailer wheels before the tractor wheels
- C. Every brake application spends air, so pumping empties the tanks faster
- D. Pumping has no effect at all on an air brake system
Show answer and explanation
Answer: C. Every brake application spends air, so pumping empties the tanks faster
This is the habit drivers bring over from cars. In a hydraulic system pumping can build pressure back up, but an air system works the other way, because each press of the pedal releases air from the tanks and you cannot get it back. When air is already low, fanning the pedal spends what little you have left. Use steady pressure, slow down and park.
9. Complete the sentence.
Before you can take the skills test for a first time Class A or Class B licence, federal rules require you to finish _____ with a school listed on the federal Training Provider Registry.
Options for blank 1: entry level driver training, a defensive driving course, a hazmat awareness course, a medical examination
Show answer and explanation
Answer: entry level driver training
Entry level driver training has been required since February 2022. It applies to a first time Class A or Class B licence, an upgrade from Class B to Class A, and the first time you go for the passenger, school bus or hazmat endorsement. The training has a theory part and a behind the wheel part, and the provider reports your completion to the registry before your state will schedule the skills test.
10. Two air lines run from the tractor to the trailer. What does the emergency line do?
- A. It carries air only while you are pressing the brake pedal
- B. It vents air out of the trailer tanks when you park
- C. It is a spare line used only if the service line fails
- D. It charges the trailer air tanks and controls the trailer emergency brakes
Show answer and explanation
Answer: D. It charges the trailer air tanks and controls the trailer emergency brakes
The emergency line, usually the red one, keeps the trailer supplied with air and holds the emergency brakes off. If it loses pressure, for example because the trailer breaks away or a line rips out, the trailer brakes come on by themselves. The service line, usually the blue one, only carries air when you press the brake pedal or use the trailer hand valve. Cross the two lines and you can drive off with no trailer brakes at all.
11. As you take a right turn in a tractor trailer, the trailer's rear wheels
- A. follow a shorter path than the tractor's front wheels, so you have to swing wide
- B. follow exactly the same path as the tractor's front wheels
- C. follow a wider path than the tractor's front wheels
- D. lift clear of the road until the turn is finished
Show answer and explanation
Answer: A. follow a shorter path than the tractor's front wheels, so you have to swing wide
This is off-tracking, and the longer the vehicle the more of it you get. The fix is to turn wide as you complete the turn, not before it: keep the rear of your vehicle close to the curb, drive forward until the front wheels are well past the corner, then turn. Swinging left first invites a car to slip up the right side, and that is exactly where your trailer is about to go.
12. Which of the following lower the risk of rolling a loaded trailer over?
Select all that apply.
- A. Keeping the cargo as low as you can
- B. Keeping the load centered over the axles and balanced side to side
- C. Slowing down before you enter a curve or an exit ramp and staying slow through it
- D. Putting the heaviest cargo on top so the weight spreads out
- E. Braking hard in the middle of the curve if the trailer starts to feel light
- F. Taking exit ramps at the posted speed, since ramp speeds are set for trucks
Show answer and explanation
Answer: A. Keeping the cargo as low as you can, B. Keeping the load centered over the axles and balanced side to side, C. Slowing down before you enter a curve or an exit ramp and staying slow through it
Rollovers account for a large share of the crashes that kill truck drivers, and most of them come down to two things: a load carried too high and too much speed in a curve. A high center of gravity tips long before the driver feels anything wrong, and the trailer can go over while the tractor still feels planted. Posted ramp speeds are set for cars, so a loaded rig often has to be well under them.
13. You want to drive a single vehicle with a gross vehicle weight rating of 26,001 pounds or more, and you will not tow anything heavier than 10,000 pounds. Which class of CDL covers that?
- A. Class A
- B. Class B
- C. Class C
- D. No CDL is required
Show answer and explanation
Answer: B. Class B
Class B is the single heavy vehicle license, such as a straight truck, a dump truck or a large bus, and it lets you tow a trailer up to 10,000 pounds. Class A covers combinations with a gross combination weight rating of 26,001 pounds or more where the towed unit is over 10,000 pounds. Class C covers smaller vehicles that fall outside A and B but carry 16 or more people including the driver, or carry hazardous materials in amounts that need placards. The higher class also lets you drive the lower ones, as long as you hold the right endorsements.
14. Which of these require a separate endorsement on your CDL?
Select all that apply.
- A. Hauling hazardous materials in amounts that require placards
- B. Driving a school bus
- C. Driving after dark
- D. Driving a tank vehicle
- E. Driving across a state line
- F. Towing a trailer under 10,000 pounds
Show answer and explanation
Answer: A. Hauling hazardous materials in amounts that require placards, B. Driving a school bus, D. Driving a tank vehicle
An endorsement is permission added to your license for a specific kind of load or vehicle, and each one has its own knowledge test. The common ones are H for hazardous materials, N for tank vehicles, P for passengers, S for school bus, T for doubles and triples, and X for a tank carrying hazardous materials. The hazardous materials endorsement also needs a security threat assessment, so it takes longer to get. Restrictions work the other way and take something away, for example an L restriction if you never passed the air brake test.
15. Complete the sentence.
A driver of a commercial motor vehicle is considered to be under the influence at a blood alcohol concentration of _____ or higher, and may not drink alcohol within _____ hours of going on duty.
Options for blank 1: 0.02, 0.04, 0.08, 0.10
Options for blank 2: 2, 4, 8, 12
Show answer and explanation
Answer: 0.04, 4
The commercial limit is half the usual limit for car drivers, and a reading between 0.02 and 0.039 still puts you out of service for 24 hours even though it is under the legal limit. Refusing a required test counts the same as failing it. A first major offense such as this one disqualifies you for at least a year, three years if you were hauling placarded hazardous materials, and a second major offense is a lifetime disqualification.
What the CDL knowledge test actually covers
There is no single national CDL exam. Your state gives the test, and nearly every state writes it from the AAMVA model Commercial Driver License Manual, which it republishes for free as its own CDL manual. So the most useful thing a CDL practice test can do is send you back to that book, because your real questions are written from it. Download your state's current manual first.
Which tests you sit depends on what you want to drive. Everyone takes general knowledge. You add air brakes if your vehicle has them, combination vehicles for a Class A, and a separate test for each endorsement such as tank, passenger, school bus or hazardous materials. The number of questions and the passing score are set by your state, and eighty percent is a common pass mark, so read your state licensing page rather than a number you found online.
There is paperwork around the test as well. You need a commercial learner's permit before you can practice on public roads, and most states make you hold it for a waiting period first. Interstate drivers need a current medical examiner's certificate on file. New Class A and Class B applicants, and applicants for the hazardous materials, passenger and school bus endorsements, also have to complete entry level driver training with a provider listed on the federal Training Provider Registry.
How to use this sampler
This set samples across the whole knowledge test instead of going deep on one part. Six questions are general knowledge, three are the headline air brake facts, three are combination vehicle basics, and three are the rules and paperwork that come up no matter which class you are after. It is a map, not a full course, so use it to find out which chapter of your manual you are weakest in.
Take it in one sitting without notes, then read the explanation for every question, including the ones you got right. Treat a wrong answer as a topic rather than a fact. If you missed the low air pressure question, do not just memorize the number, go and read the whole air brakes chapter, because the test asks the same idea from several directions.
The three quizzes linked below go deeper on general knowledge, air brakes and combination vehicles. Run this one first to see where you stand, then run the one that matches the test you are actually scheduled for. Reading your manual out loud, one section at a time, and then answering questions on that section is slower than skimming and works far better.
How StudyPDF turns your state CDL manual into full practice tests
Fifteen questions can show you where you are shaky. They cannot get you ready on their own, and no generic bank matches your state's manual, which is the exact book your examiner writes from.
StudyPDF works from your material instead. You upload your state's CDL manual PDF, your training school handouts or the endorsement chapters you care about, and Bo, the study agent, builds full-length practice tests from those exact pages. Every question is grounded in your document, and every explanation cites where the answer came from, so you can jump straight to the page when something looks wrong. You can regenerate fresh tests as often as you like, narrow them to one section such as air brakes or cargo securement, and track which topics you keep missing.
You do not need a file to start. If you have nothing to upload yet, just name a topic, for example combination vehicle coupling or hours of service, and Bo writes a practice test on it. Starting is free.
Written by the StudyPDF team. Last updated 2026-08-19.