Free Hawaii DMV CDL — Air Brakes Practice Test 2026
The Hawaii CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official Hawaii 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 Hawaii written test
The Hawaii CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official Hawaii 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 Hawaii practice questions.
How to pass the first time
- Read the official Hawaii 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.
Hawaii CDL — Air Brakes test — frequently asked questions
How many questions are on the Hawaii CDL — Air Brakes test?
The Hawaii 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 Hawaii 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 Hawaii 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 Hawaii 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 Hawaii 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 Hawaii driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Hawaii practice tests
Take the CDL — Air Brakes test in another state
Every Hawaii question is written from the official Hawaii 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
Hawaii CDL — Air Brakes questions with answers
20 sample questions from the Hawaii 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. The governor on your truck stopped the compressor at about 125 psi. A few brake applications later the gauge reads 110 psi. Is the compressor pumping yet?
Correct answer: No, it stays idle until pressure falls to the cut-in level, around 100 psi
After cut-out, the governor does not let pumping resume until tank pressure has dropped to the cut-in level, which is around 100 psi. At 110 psi the compressor is still idle.
Source: Hawaii Commercial Driver License Manual — Section 5.1.2, Air Compressor Governor
2. On Hawaii's vehicle inspection test, the parking brake check is done with the air system in what state?
Correct answer: Built up to governor cut-out
Section 11 has you bring the air pressure up to governor cut-out, set the parking brake, and gently try to pull forward to see that the brake holds the vehicle.
Source: Hawaii Commercial Driver License Manual — Section 11.1.2, Cab Check/Engine Start
3. A driver keeps leaning on fading brakes instead of easing the load on them. Where does the manual say continued overuse can lead?
Correct answer: Fade can worsen to the point where the vehicle can no longer be slowed or stopped
Overusing the service brakes overheats them, and continued overuse can deepen the fade until there is not enough braking left to slow or stop the vehicle.
Source: Hawaii Commercial Driver License Manual — Section 5.4.5, Brake Fading or Failure
4. For the Z restriction, how does the manual define air over hydraulic brakes?
Correct answer: A system that works partly on the air brake principle and partly on the hydraulic principle
For the skills test and the Z restriction, air over hydraulic means a braking system that runs partly on air and partly on hydraulics. A driver tested in one is restricted from vehicles whose brakes run fully on air.
Source: Hawaii Commercial Driver License Manual — Section 1, CDL Endorsements & Restrictions
5. Which of these is NOT part of the manual's braking technique for a long downgrade once you are in the proper low gear?
Correct answer: Hold light, steady pedal pressure the whole way down
The technique is a cycle: brake until you are about 5 mph under your safe speed, release, let speed return to the safe speed, and repeat. Holding steady pressure all the way down is not part of it, because the brakes only supplement engine braking.
Source: Hawaii Commercial Driver License Manual — Section 5.4.6, Proper Braking Technique
6. Which of these is NOT something Section 11 tells you to look for when you inspect a drum brake?
Correct answer: A manufacturer's date stamp newer than 1998
The drum brake check covers cracks, dents and holes, loose or missing bolts, and contaminants such as debris, oil or grease. A date stamp is not part of it.
Source: Hawaii Commercial Driver License Manual — Section 11.2.3, Brakes
7. You are ready to pull away in a newer air-braked truck, and the yellow, diamond-shaped parking brake knob is pulled out. What do you do to release the spring brakes?
Correct answer: Push the knob in
The push-pull knob works one way for each job: out sets the parking (spring) brakes, and in releases them.
Source: Hawaii Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
8. Your low air warning activates while you are driving. Besides telling you to stop, what does the manual say it might be a sign of?
Correct answer: An air leak in the system
A low air warning may mean air is leaking out of the system. Stop and park safely as soon as you can, while there is still air for the foot brakes.
Source: Hawaii Commercial Driver License Manual — Section 5.4.7, Low Air Pressure
9. Hawaii's restriction list includes Code L and Code Z, and both concern air brakes. How do they differ?
Correct answer: Code L bars air brake equipped CDL vehicles, while Code Z bars only CDL vehicles with full air brakes
Hawaii lists Code L as no air brake equipped CDL vehicle and Code Z as no CDL vehicle with full air brakes. Section 1 explains that Z follows a skills test taken in an air over hydraulic vehicle, so it is the narrower of the two.
Source: Hawaii Commercial Driver License Manual — Hawaii Commercial Driver License Program, What CDL Restrictions Could I Receive?
10. Compared with a vehicle that has hydraulic brakes, which extra distance does an air-braked vehicle add to its total stopping distance?
Correct answer: Brake lag distance
Perception, reaction and braking distance apply to any vehicle. Brake lag distance is the added piece for air brakes, covering the time the air needs to reach the brakes.
Source: Hawaii Commercial Driver License Manual — Section 5.4.4, Stopping Distance
11. Where does the s-cam in an s-cam brake get its name?
Correct answer: From its shape, which looks like the letter S
The cam is called an s-cam because of its S-like shape. When the camshaft twists, the cam spreads the brake shoes against the drum.
Source: Hawaii Commercial Driver License Manual — Section 5.1.8, Foundation Brakes
12. You park an air-braked truck with the spring brakes set. Over the weekend a slow leak empties the air tanks. What holds the truck?
Correct answer: The springs, which hold the brakes on mechanically and need no air to do it
Parking and emergency brakes have to be held on mechanically because air can leak away over time. Spring brakes do this: air pressure holds the springs back while you drive, and with the air gone the springs keep the brakes applied.
Source: Hawaii Commercial Driver License Manual — Section 5.1.14, Spring Brakes
13. The manual says a dead low pressure warning signal plays out differently depending on the kind of air system. Which pairing is right?
Correct answer: Single-circuit: sudden emergency braking; dual: longer stopping distance, with limited braking before the spring brakes apply
Without a working warning you could lose air and never know it. In a single-circuit system that could bring sudden emergency braking. In a dual system the stopping distance grows, and only limited braking is left before the spring brakes apply.
Source: Hawaii Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
14. Brake lag is a delay that comes with air brakes. On which vehicles does the manual say hydraulic brakes, which work instantly, are used?
Correct answer: Cars and light or medium trucks
Hydraulic brakes, found on cars and on light and medium trucks, act at once. Air brakes take at least half a second while the air travels through the lines.
Source: Hawaii Commercial Driver License Manual — Section 5.4.4, Stopping Distance
15. On the vehicle inspection test you check a belt-driven air compressor's belt for snugness. How much play at the center of the belt does the manual allow?
Correct answer: 1/2 to 3/4 inch
Section 11 lists the air compressor belt among the belts to check for snugness, meaning 1/2 to 3/4 inch of play at the center, along with cracks, frays and other wear.
Source: Hawaii Commercial Driver License Manual — Section 11.1.1, Engine Compartment (Engine Off)
16. The modulating control valve handle found on some dashboards is spring-loaded. What does the manual say the spring loading gives the driver?
Correct answer: A feel for the braking action
The modulating valve is spring-loaded so the driver can sense how much braking is being applied. Moving the lever farther brings the spring brakes on harder.
Source: Hawaii Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
17. Which of these is NOT a kind of low air pressure warning the manual describes?
Correct answer: The brake lights flashing on their own
The manual describes a warning light, usually red, a buzzer that may sound with it, and the wig wag's mechanical arm. Brake lights are worked by the stop light switch when you brake and are not a low air warning.
Source: Hawaii Commercial Driver License Manual — Section 5.1.11, Low Air Pressure Warning
18. You are slowing with the brake pedal and need more braking. What happens when you push the pedal down harder?
Correct answer: More air pressure goes to the brakes
The pedal (the manual also names it the foot valve or the treadle valve) meters air to the brakes. Pressing harder sends more air pressure, and easing off lowers it and releases the brakes.
Source: Hawaii Commercial Driver License Manual — Section 5.1.7, The Brake Pedal
19. Your brakes are too hot to set the parking brakes, so you will hold the truck with wheel chocks. On what kind of surface does the manual say to use them?
Correct answer: A level surface
When the parking brakes should not be used, the manual says to chock the wheels on level ground. Let hot brakes cool before you set the parking brakes.
Source: Hawaii Commercial Driver License Manual — Section 5.4.8, Parking Brakes
20. An older vehicle's compressor governor cuts out at 120 psi. Under the manual's alternate rule for older vehicles, the visible low air warning must come on before pressure falls below what level?
Correct answer: 60 psi
For older vehicles the manual gives the mark as one half of the governor's cut-out pressure instead of 55 psi. Half of 120 psi is 60 psi.
Source: Hawaii Commercial Driver License Manual — Section 5.1.11, Low Air Pressure Warning