Free North Dakota DMV CDL — Air Brakes Practice Test 2026
The North Dakota CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official North Dakota driver handbook — every one has a clear explanation, and you can retake as often as you like with no sign-up.
Content reviewed against official driver handbooks · August 12, 2026
What's on the North Dakota written test
The North Dakota CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official North Dakota exam format — always confirm current details with your state DMV.
Practice by topic
Focus on one area at a time — each topic has its own set of North Dakota practice questions.
How to pass the first time
- Read the official North Dakota driver handbook at least once before test day.
- Practice by topic to find your weak spots, then fix them.
- Take full-length practice tests until you pass comfortably every time.
- Read every explanation — understanding beats memorizing.
North Dakota CDL — Air Brakes test — frequently asked questions
How many questions are on the North Dakota CDL — Air Brakes test?
The North Dakota CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Our practice tests mirror that format.
How many questions can I miss on the North Dakota CDL — Air Brakes test?
You can miss up to ~5 of the ~25 questions and still pass — you need ~20 correct, which is 80%.
Can I retake the practice test?
Yes — practice as often as you like, completely free. The questions and answer choices are shuffled each time.
Can I take the North Dakota practice test in Spanish?
Yes. Every question here is available in English and Spanish — switch languages anytime. Many states also offer the real knowledge test in languages other than English; confirm what North Dakota offers with your DMV.
Can I practice on my phone?
Yes. The practice tests work in any mobile or desktop browser — no app or sign-up needed — so you can study anywhere.
Are these the real DMV test questions?
No. Our questions are original, written from the current official North Dakota driver handbook to match the real test's topics and style. We are not affiliated with any DMV or government agency.
What's the best way to study?
Read the North Dakota driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other North Dakota practice tests
Take the CDL — Air Brakes test in another state
Every North Dakota question is written from the official North Dakota driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free
North Dakota CDL — Air Brakes questions with answers
20 sample questions from the North Dakota CDL — Air Brakes question bank — each with the correct answer, a short explanation, and the section of the official handbook it comes from.
Show all 20 questions with answers
1. In the modernized air leakage rate test, a straight truck is pulling a trailer that has no air brakes. With the foot brake held for one minute after the gauge stabilizes, what is the most the pressure may drop?
Correct answer: Three pounds, the same limit as a single vehicle
Section 11M groups a single vehicle and a trailer without air brakes together at no more than three pounds in one minute. The four-pound limit is the one for a combination vehicle.
Source: North Dakota Commercial Driver License Manual — Section 11M, Air Brake or Hydraulic Brake Check
2. Your brakes are very wet and the temperature is below freezing. What does the manual say can happen if you set the parking brakes now?
Correct answer: They can freeze up and leave the vehicle stuck
Very wet brakes can freeze when the parking brakes are applied in freezing weather, and then the vehicle will not move. The manual says to hold the vehicle with wheel chocks instead.
Source: North Dakota Commercial Driver License Manual — Section 5.4.8, Parking Brakes
3. Among North Dakota's numbered tips for preparing for the CDL road test, what does the manual say you must do to avoid an "airbrakes" restriction?
Correct answer: Take the test in a vehicle that has a full air brake system
The road test tips say that avoiding the airbrakes restriction means testing in a vehicle with a full air brake system. The other tips deal with different restrictions, such as the automatic transmission restriction and the restricted Class A issued after a test in a truck and trailer.
Source: North Dakota Commercial Driver License Manual — North Dakota Information, Preparing for the Road Test
4. Something has gone wrong, and tank pressure keeps climbing well past the governor's usual cut-out level. At what pressure does the manual say the safety relief valve typically opens?
Correct answer: 150 psi
The safety valve sits in the first tank the compressor feeds and guards the whole system against too much pressure; its usual setting is 150 psi. If it releases air, something is wrong and a mechanic should fix the fault.
Source: North Dakota Commercial Driver License Manual — Section 5.1.6, Safety Valve
5. How many factors does the manual add together to get total stopping distance for a vehicle with air brakes?
Correct answer: Four
Air brakes add brake lag distance to the perception, reaction and braking distances, so four factors make up the total. The lag exists because air needs a half second or more to travel through the lines and reach the brakes.
Source: North Dakota Commercial Driver License Manual — Section 5.4.4, Stopping Distance
6. Automatic air tank drains are available with electric heating devices. What does the manual say the heaters are for?
Correct answer: Helping keep the automatic drain from freezing in cold weather
Automatic drains expel water and oil on their own, but the drain itself can freeze. The manual says electric heating devices are available to help stop that from happening in cold weather.
Source: North Dakota Commercial Driver License Manual — Section 5.1.4, Air Tank Drains
7. Many brake systems are built so that pressing the brake pedal while the spring brakes are on will not damage the brakes. Why does the manual still tell you to make a habit of staying off the pedal?
Correct answer: Some systems lack that protection, and the protection can fail where it is fitted
Spring force and air pressure acting together can damage the brakes. Because the safeguard is not on every system and is not guaranteed to work, the manual says the better practice is never to push the pedal down while the spring brakes are applied.
Source: North Dakota Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
8. North Dakota's manual prints the air brake check for both its older vehicle inspection test and the modernized skills test the state began phasing in. How do the two versions break the check down?
Correct answer: The older version lists three components; the modernized version lists four parts
The older pre-trip material breaks the air brake inspection into three components. Section 11M's modernized check has four parts: the air gauge and governor cutout check, the air leakage rate test, the air warning device test and the emergency brake test. In either version, getting the air brake check wrong fails the vehicle inspection test automatically.
Source: North Dakota Commercial Driver License Manual — Section 11M, Air Brake or Hydraulic Brake Check
9. A bus with dual parking control valves has lost its main air pressure, and the driver pushes in the spring-loaded control to release the spring brakes and move. What happens when the driver lets go of that control?
Correct answer: The spring brakes come back on
That control is held in the out position by a spring. Pushing it in sends air from the separate tank to release the spring brakes, and letting go allows them to apply again. The separate tank holds enough air for only a few such releases.
Source: North Dakota Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
10. An average driver at 55 mph in an air-braked vehicle has good traction and good brakes. What does the manual give as the total stopping distance?
Correct answer: Over 450 feet
The total includes perception, reaction, brake lag and braking distance, and at 55 mph the manual puts it at more than 450 feet. Brake lag alone adds about 32 feet at that speed on dry pavement.
Source: North Dakota Commercial Driver License Manual — Section 5.4.4, Stopping Distance
11. On a vehicle with automatic slack adjusters, a pushrod stroke beyond the legal adjustment limit points to one of several things. Which of these is NOT one the manual names?
Correct answer: A governor cut-out pressure that is set too high
The manual lists three possibilities: a mechanical problem in the adjuster, a problem in the foundation brake components that go with it, or an adjuster that was not installed properly. Governor settings are not part of that list.
Source: North Dakota Commercial Driver License Manual — Section 5.3.2, During Step 5 Walkaround Inspection
12. The manual says never to leave your vehicle unattended without doing one of two things. Which pair is it?
Correct answer: Setting the parking brakes or putting chocks at the wheels
An unsecured vehicle could roll off and hurt someone or damage property, so the manual wants the parking brakes applied or the wheels chocked whenever the vehicle is left unattended.
Source: North Dakota Commercial Driver License Manual — Section 5.4.8, Parking Brakes
13. North Dakota's manual says Class A, B and C drivers are restricted from air-brake-equipped commercial vehicles until they pass a knowledge test on air brakes plus a skill test. What kind of vehicle does it say the skill test must be taken in?
Correct answer: One that has a full or a partial air brake system
The airbrakes restriction paragraph keeps the restriction in place until the driver passes the knowledge test and also a skill test taken in a vehicle that has a full or a partial air brake system. The manual's restriction list separately carries code L (no air-brake-equipped CMV) and code Z (no full air-brake-equipped CMV).
Source: North Dakota Commercial Driver License Manual — North Dakota Information, Airbrakes Restriction
14. You are making an emergency stop with the controlled braking method. In which situation does the manual say to release the brakes?
Correct answer: When you need a larger steering adjustment or the wheels lock
Controlled braking means braking as hard as possible short of wheel lockup while keeping steering movements very small. A bigger steering correction or a wheel lockup is the cue to let off, then brake again as soon as you can.
Source: North Dakota Commercial Driver License Manual — Section 5.4.3, Emergency Stops
15. You are in the proper low gear on a long downgrade, and your speed has climbed to your "safe" speed. How hard does the manual say to apply the brakes?
Correct answer: Firmly enough that you feel a definite slowing
The technique is to brake hard enough to feel the vehicle clearly slow, let off at about 5 mph under the safe speed, and repeat once speed climbs back to the safe speed.
Source: North Dakota Commercial Driver License Manual — Section 5.4.6, Proper Braking Technique
16. In the first component of North Dakota's three-component air brake check, you build pressure to governed cut-out, shut off the engine, and then turn the key back to "on." Why does the manual have you turn the key on?
Correct answer: So the gauges work while you watch for a pressure drop
The first component is done with the engine shut off, and the key goes back to the on position so the gauges still read. You then push in the controls, press the foot brake all the way down and hold it for a minute while watching the air gauge.
Source: North Dakota Commercial Driver License Manual — Section 11.1.2, Cab Check/Engine Start
17. In stab braking you release the brakes when the wheels lock and reapply once they roll. After the release, how long does the manual say it can take the wheels to start rolling?
Correct answer: Up to one second
The manual notes that the wheels may need as much as a second to begin rolling again. Braking again before they roll keeps the vehicle from straightening out.
Source: North Dakota Commercial Driver License Manual — Section 5.4.3, Emergency Stops
18. Brakes are built to take a lot of heat, yet they can fade or fail from too much of it. What driving habit does the manual blame for that excessive heat?
Correct answer: Using the brakes too much instead of relying on engine braking
Overusing the service brakes overheats them, and that leads to fade. On a long or steep downgrade the brakes are meant only to add to the engine's braking effect.
Source: North Dakota Commercial Driver License Manual — Section 5.4.5, Brake Fading or Failure
19. Only your tractor has ABS; the trailer does not. During hard braking, what does the manual tell you to keep an eye on?
Correct answer: The trailer, easing off the brakes if you safely can when it starts to swing out
With ABS on the tractor only, you should keep steering control and are less likely to jackknife, but the trailer can still swing. The manual says to watch it and ease off the brakes, if that can be done safely, when it begins to swing out.
Source: North Dakota Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
20. North Dakota's Air Brakes section says a low air pressure warning must come on before tank pressure falls below 60 psi. What kind of signal does it require?
Correct answer: A signal the driver can see, usually a red light
The required warning is one the driver can see, and the manual says a red light is the usual form, with a buzzer possibly sounding too. On older vehicles the threshold may instead be one-half of the governor cut-out pressure.
Source: North Dakota Commercial Driver License Manual — Section 5.1.11, Low Air Pressure Warning