Free New Hampshire DMV CDL — Air Brakes Practice Test 2026
The New Hampshire CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official New Hampshire 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 New Hampshire written test
The New Hampshire CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official New Hampshire 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 New Hampshire practice questions.
How to pass the first time
- Read the official New Hampshire 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.
New Hampshire CDL — Air Brakes test — frequently asked questions
How many questions are on the New Hampshire CDL — Air Brakes test?
The New Hampshire 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 New Hampshire 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 New Hampshire 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 New Hampshire 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 New Hampshire 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 New Hampshire driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other New Hampshire practice tests
Take the CDL — Air Brakes test in another state
Every New Hampshire question is written from the official New Hampshire 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
New Hampshire CDL — Air Brakes questions with answers
20 sample questions from the New Hampshire 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. Your truck has a manual-reset wig wag. With system pressure still at 45 psi, you push the arm up out of your line of sight. What does the manual say will happen?
Correct answer: The arm will not stay put until pressure is back above 55 psi
A wig wag drops a mechanical arm into view when system pressure goes under 55 psi. The manual-reset kind has to be put back by hand, and it will not hold in the out-of-view position while pressure remains below that level.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.11, Low Air Pressure Warning
2. On the vehicle inspection test, you check that the power unit's parking brake holds a combination vehicle. What state should the trailer brakes be in for that check?
Correct answer: Released
The parking brake check is done with the parking brake engaged and, on combination vehicles, the trailer brakes released. With your foot off the service brake you pull gently forward to see that the parking brake alone holds the vehicle.
Source: New Hampshire Commercial Driver's License Manual — Section 11.1.1, Parking and Trailer Brake Check
3. Each time you let up on the brake pedal, some compressed air leaves the system and tank pressure drops. What does the manual say makes up for the lost air?
Correct answer: The air compressor
Releasing the brakes vents some compressed air and lowers tank pressure, and the compressor has to pump that air back. That is why needless pedal work can drain air more quickly than the compressor restores it.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.7, The Brake Pedal
4. On the CDL vehicle inspection checklists printed in the manual, under which heading does the air brake check appear?
Correct answer: In-Vehicle/Engine Start
Each checklist puts the air or hydraulic brake check first under In-Vehicle/Engine Start, ahead of the parking and trailer brake check and the service brake check. It is starred, meaning an automatic failure if it is not performed correctly.
Source: New Hampshire Commercial Driver's License Manual — Section 11, Class A Checklist
5. Section 2 gives a minimum total stopping distance of 419 feet at 55 mph. The Air Brakes section gives a total of more than 450 feet at the same speed. What accounts for the difference?
Correct answer: Brake lag, which adds about 32 feet at 55 mph on dry pavement
Air takes a little time to travel through the lines after the pedal is pressed, so air-braked vehicles add a fourth piece, brake lag distance, to perception, reaction and braking distance. At 55 mph that lag is worth roughly 32 feet, which lifts the total past 450 feet.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.4, Stopping Distance
6. A failed low pressure warning lets air leak away without your noticing. The manual says a dual system will then need a longer stopping distance. What does it add about the braking you have left?
Correct answer: Only limited braking is possible before the spring brakes come on
Without a working warning you would not know the pressure was dropping. In a single-circuit system that could bring on sudden emergency braking. In dual systems the stopping distance grows, and the manual adds that you get only a limited amount of braking before the spring brakes apply.
Source: New Hampshire Commercial Driver's License Manual — Section 5.3.3, Step 7 Final Air Brake Check
7. The manual says to use the parking brakes any time you park, with two exceptions. Which pair is it?
Correct answer: Very hot brakes, and very wet brakes in freezing temperatures
Parking brakes applied while very hot can be damaged by the heat, and applied while very wet in freezing weather they can ice up and leave the vehicle stuck. In those cases the manual has you hold the vehicle with wheel chocks on a level surface instead.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.8, Parking Brakes
8. The ABS requirement reached air-braked truck tractors before it reached other air-braked vehicles such as trucks, buses, trailers and converter dollies. How far apart are the two build dates?
Correct answer: One year
Air-braked truck tractors need ABS if they were built on March 1, 1997 or later. For the other air-braked vehicles the date is March 1, 1998, exactly one year after that.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.16, Antilock Braking Systems (ABS)
9. The manual lists what puts the L restriction, no air brake equipped CMV, on a CLP or CDL. Which of these is NOT one of the triggers?
Correct answer: Taking the skills test in a vehicle with an automatic transmission
The L restriction follows from skipping or failing the knowledge test's air brake component, or from doing the skills test in a vehicle without air brakes. Testing in an automatic leads to a different restriction, E, which concerns manual transmissions.
Source: New Hampshire Commercial Driver's License Manual — Section 1, Restrictions
10. You are in the proper low gear on a long downgrade and have picked 35 mph as your "safe" speed. Following the manual's braking technique, about what speed should you be down to when you release the brakes?
Correct answer: About 30 mph
You brake firmly enough to feel the truck clearly slow and let off when you are roughly 5 mph under your safe speed, here about 30 mph. You then wait for speed to climb back to 35 mph before braking again.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.6, Proper Braking Technique
11. The manual calls hitting the brakes a good response when someone suddenly pulls out ahead of you, but only under two conditions. What are they?
Correct answer: You have room to stop, and you apply the brakes the right way
Braking is the natural reaction, and the manual accepts it when the distance is sufficient and the brakes are used correctly. That means braking so the vehicle stays in a straight line and can still be steered, using controlled braking or stab braking.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.3, Emergency Stops
12. While you are driving an air-braked truck normally, what keeps the spring brakes from applying?
Correct answer: Air pressure holding the springs back
Spring brakes use strong springs that air pressure holds back during driving. Take the air away, whether with the parking brake control or through a leak that drains the system, and the springs put the brakes on.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.14, Spring Brakes
13. Which order matches the manual's service brake test at the end of the final air brake check?
Correct answer: Let air pressure reach normal, take the parking brake off, ease forward at about 5 mph, then brake firmly with the pedal
This last test is done on the move at low speed once pressure is normal and the parking brake is off. While braking firmly you watch for pulling to one side, an odd feel, or a slow response. Pulling against a set parking brake is the separate parking brake test.
Source: New Hampshire Commercial Driver's License Manual — Section 5.3.3, Step 7 Final Air Brake Check
14. Driver A's CDL carries the L restriction and Driver B's carries the Z restriction. Going by the manual's definitions, which of them may operate a commercial vehicle with air over hydraulic brakes?
Correct answer: Driver B only
L bars any commercial vehicle with any type of air brakes, and the manual counts systems that run on air either entirely or in part. Z bars only vehicles whose brakes work fully on the air brake principle, so a Z-restricted driver can still drive one with air over hydraulic brakes.
Source: New Hampshire Commercial Driver's License Manual — Section 1, Restrictions
15. Controlled braking and stab braking are both emergency-stop methods. How does the way you first apply the brakes differ between them?
Correct answer: Controlled braking is as hard as possible without locking the wheels; stab braking is all the way on until the wheels lock
With controlled braking you brake hard but stay just short of lockup, releasing only if the wheels lock or you need a bigger steering correction. With stab braking you apply fully, let off when the wheels lock, and apply fully again once they are rolling.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.3, Emergency Stops
16. Section 5 covers brakes that are too hot or too wet to set the parking brakes on. Which pairing of condition and remedy matches the manual?
Correct answer: Very hot brakes: let them cool first. Wet brakes: drive in a low gear with light brake pressure until they heat up and dry
Hot brakes should be allowed to cool before the parking brakes are used, since the heat can damage them. Wet brakes can be dried by braking lightly while driving in a low gear, which matters in freezing weather because wet parking brakes can freeze.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.8, Parking Brakes
17. Several faults described in the Air Brakes section are handed to a mechanic or a repair facility. Which of these tasks does the manual say you must do yourself?
Correct answer: Draining manually operated air tanks once each day of driving is over
Tanks with manual drain valves, worked by a quarter turn or a pull cable, have to be drained by the driver when the day's driving ends. By contrast, a safety valve that releases air goes to a mechanic, and a brake with an automatic adjuster found out of adjustment goes to a repair facility.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.4, Air Tank Drains
18. After the low air pressure warning comes on, how long does the manual say controlled braking stays possible?
Correct answer: Only while enough air is left in the tanks
A warning may mean an air leak, and the remaining air is what lets you brake under control. Once pressure sinks into the 20 to 45 psi range the spring brakes apply on their own, so the manual says to stop and park safely as soon as you can.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.7, Low Air Pressure
19. What does the manual warn could happen if you walk away from your vehicle without setting the parking brakes or chocking the wheels?
Correct answer: It could roll off and hurt someone or damage property
The rule is never to leave the vehicle unattended unless the parking brakes are applied or the wheels are chocked. Otherwise the vehicle may roll, injuring people and causing damage.
Source: New Hampshire Commercial Driver's License Manual — Section 5.4.8, Parking Brakes
20. The manual lists several reasons you might need more application pressure than before. Which of these is NOT one of them?
Correct answer: An alcohol evaporator that has run dry
Needing more application pressure to hold the same speed points to fading brakes, and the manual adds that out-of-adjustment brakes, air leaks or mechanical problems can also be behind it. An empty alcohol evaporator is a cold-weather icing concern and is not on that list.
Source: New Hampshire Commercial Driver's License Manual — Section 5.1.10, Application Pressure Gauge