Free Alaska DMV CDL — Air Brakes Practice Test 2026
The Alaska CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official Alaska 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 Alaska written test
The Alaska CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official Alaska 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 Alaska practice questions.
How to pass the first time
- Read the official Alaska 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.
Alaska CDL — Air Brakes test — frequently asked questions
How many questions are on the Alaska CDL — Air Brakes test?
The Alaska 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 Alaska 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 Alaska 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 Alaska 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 Alaska 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 Alaska driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Alaska practice tests
Take the CDL — Air Brakes test in another state
Every Alaska question is written from the official Alaska 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
Alaska CDL — Air Brakes questions with answers
20 sample questions from the Alaska 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. Newer air-braked vehicles use a yellow, diamond-shaped parking brake knob. What does the manual say the control may be on older vehicles?
Correct answer: A round blue knob or a lever
The manual says an older vehicle's control might be a blue, round knob, or it might be shaped differently altogether, such as a lever you swing sideways or up and down.
Source: Alaska Commercial Driver License Manual — Section 5.4.8, Parking Brakes
2. How does a wedge brake force its shoes against the drum?
Correct answer: The chamber's push rod drives a wedge between the ends of the shoes
In a wedge brake the chamber's push rod shoves a wedge straight between the shoe ends, spreading them against the drum. A wedge brake may have one brake chamber or two, and it may self-adjust or need manual adjustment.
Source: Alaska Commercial Driver License Manual — Section 5.1.8, Foundation Brakes
3. On a long grade, overheated brake drums expand. What does the manual say this does to the brake shoes and linings?
Correct answer: They have to travel farther to reach the drum and press on it with less force
As the drums grow with heat, the shoes and linings must move a greater distance before touching them, and they push with reduced force. If the overuse continues, fade can build until the vehicle can't be slowed or stopped.
Source: Alaska Commercial Driver License Manual — Section 5.4.5, Brake Fading or Failure
4. Bus drivers earn the passenger endorsement through a knowledge test covering Sections 2 and 4. What does the manual add when the bus has air brakes?
Correct answer: A knowledge test on Section 5, Air Brakes
Section 4 says the passenger endorsement requires testing on Sections 2 and 4, and that a driver whose bus has air brakes must pass a test on Section 5 as well, along with the skills tests for the vehicle class.
Source: Alaska Commercial Driver License Manual — Section 4, Transporting Passengers Safely
5. You are descending a long grade in the proper low gear and braking the way the manual describes. About how long should each brake application last?
Correct answer: About three seconds
The technique is to brake until you are about five mph under your 'safe' speed, which should take roughly three seconds, then release and let speed return to the 'safe' speed before braking again.
Source: Alaska Commercial Driver License Manual — Section 5.4.6, Proper Braking Technique
6. Why does the manual say emergency and parking brakes have to be held on by mechanical force instead of air pressure?
Correct answer: Air pressure can leak away over time
Every truck, truck tractor and bus needs emergency and parking brakes. Because air can eventually leak out, those brakes rely on mechanical force, and spring brakes are the usual way of providing it.
Source: Alaska Commercial Driver License Manual — Section 5.1.14, Spring Brakes
7. Leaving emergencies aside, when does the manual say an automatic slack adjuster should need to be adjusted by hand?
Correct answer: Only when the brakes are being serviced or the adjusters are being installed
Automatic adjusters should not need hand adjustment except during brake maintenance and when they are installed. A pushrod stroke over the legal limit points to a mechanical problem, and adjusting by hand generally hides that problem instead of fixing it.
Source: Alaska Commercial Driver License Manual — Section 5.3.2, During Step 5 Walk-around Inspection
8. Spring brakes on tractors and straight trucks come fully on somewhere between 20 and 45 psi. What narrower range does the manual call typical?
Correct answer: 20 to 30 psi
The manual gives 20 to 45 psi as the full range and 20 to 30 psi as typical. It also warns you not to wait for that: stop safely the moment the low air warning first shows.
Source: Alaska Commercial Driver License Manual — Section 5.1.14, Spring Brakes
9. Your vehicle has air over hydraulic brakes, not a full air brake system. Under the manual's list of knowledge tests, do you take the air brakes test?
Correct answer: Yes. The test covers air brakes, air over hydraulic included
Section 1 lists the air brakes test among the CDL knowledge tests and says it is required when your vehicle has air brakes, air over hydraulic included.
Source: Alaska Commercial Driver License Manual — Section 1.1.1, Knowledge Tests
10. Total stopping distance for an air-braked vehicle is made up of four parts. Which of these is NOT one of them?
Correct answer: Cut-in distance
The four parts are perception, reaction, brake lag and braking distance. Brake lag is the piece that air brakes add, because air needs a moment to travel through the lines.
Source: Alaska Commercial Driver License Manual — Section 5.4.4, Stopping Distance
11. You work the parking brake control in the cab to park. What actually puts the spring brakes on?
Correct answer: Springs, which apply the brakes once the control lets the air out
While you drive, air pressure holds the powerful springs back. The parking brake control releases that air from the spring brakes, and the springs then apply the brakes.
Source: Alaska Commercial Driver License Manual — Section 5.1.14, Spring Brakes
12. You are driving a pre-1975 truck on an icy road and are tempted to move the front brake control to 'slippery.' What does the manual advise?
Correct answer: Leave it in 'normal,' because 'slippery' cuts stopping power and front wheels are unlikely to skid even on ice
The manual says to make sure the control is in 'normal' so you keep normal stopping power. Limiting valves cut stopping power, and tests found that braking is not likely to skid the front wheels, ice included.
Source: Alaska Commercial Driver License Manual — Section 5.1.13, Front Brake Limiting Valve
13. Your air compressor stops working while you are on the road. What does the manual say about the air already held in the storage tanks?
Correct answer: It is enough to let you use the brakes several times
Air storage tanks hold a reserve of compressed air. The manual says that reserve allows several brake applications even with the compressor out of action, which is a long way from normal braking for hours.
Source: Alaska Commercial Driver License Manual — Section 5.1.3, Air Storage Tanks
14. Alaska's restriction list names one restriction specifically for a driver whose skills-test vehicle has air over hydraulic brakes. Which one is it?
Correct answer: Z
The Z restriction, no full air brake equipped CMV, goes on the license when the test vehicle has air over hydraulic brakes. The manual adds that a driver with either the L or the Z restriction may not drive a CMV that has full air brakes.
Source: Alaska Commercial Driver License Manual — Section 1, Commercial Driver License Classes, Endorsements and Restrictions
15. A coworker says his truck is designed so spring force and air pressure can't combine, so he presses the brake pedal with the spring brakes on. How does the manual see that habit?
Correct answer: Not every system has that protection, and it can fail, so it is a habit to avoid
Pressing the pedal with the spring brakes on can damage the brakes through the combined force of springs and air. Many systems guard against this, but the manual says some don't and the safeguard can fail, so the safe habit is to stay off the pedal.
Source: Alaska Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
16. Compressed air carries some water and compressor oil into the air tanks. Where do they tend to collect?
Correct answer: At the bottom of the tank, where the drain valve is fitted
Water and oil settle toward the bottom of each air tank, and that is why every tank has its drain valve at the bottom.
Source: Alaska Commercial Driver License Manual — Section 5.1.4, Air Tank Drains
17. The manual tells drivers to use only the braking force needed to stop safely, with one exception. Who may fully apply the brakes in an emergency stop?
Correct answer: A driver whose straight truck or combination always has working ABS on all axles
Normally you brake the same way with or without ABS and ease off when you need to stay in control. The single exception the manual gives is a vehicle with working ABS on all of its axles, where the brakes can be fully applied in an emergency stop.
Source: Alaska Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
18. Which of these would NOT put an 'L' restriction on an Alaska commercial license?
Correct answer: Testing in a truck with full air brakes after passing every air brake item
Alaska places the L restriction when a driver fails the knowledge test on air brakes, cannot correctly identify the air brake components, does not conduct the air brake check properly, or tests in a vehicle that lacks a full air brake system.
Source: Alaska Commercial Driver License Manual — Section 1, Commercial Driver License Classes, Endorsements and Restrictions
19. It is below freezing, your brakes are soaked, and you will be parking soon. How does the manual say to dry them first?
Correct answer: Apply the brakes gently while driving in a low gear so they warm up and dry
Very wet brakes can freeze in cold weather and leave the vehicle unable to move, so the manual says not to set the parking brakes in that condition. Light braking in a low gear heats and dries them, and wheel chocks on level ground can hold the vehicle.
Source: Alaska Commercial Driver License Manual — Section 5.4.8, Parking Brakes
20. According to the manual, automatic slack adjusters have been on all vehicles built since what year?
Correct answer: 1994
The manual states that every vehicle built since 1994 has automatic slack adjusters. They adjust themselves during full brake applications, but they still have to be checked.
Source: Alaska Commercial Driver License Manual — Section 5.3.2, During Step 5 Walk-around Inspection