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CDL knowledge test

CDL Air Brakes Practice Test 2026

Required to drive a commercial vehicle with air brakes without the air-brake restriction: system parts, dual systems, inspecting and using air brakes.

45 practice questions, all written from Commercial Driver's License Manual (Version 07/20/2026 (form DMV 60A), AAMVA, Virginia DMV edition). Every answer shows the manual section it comes from. Free, no sign-up.

  • 45 questions
  • 25 per attempt
  • Pass mark: 80%
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Start the Air Brakes practice test

25 questions. Passing score: 80%. No sign-up needed.

Choose how you want to practice:

Test format

Passing score At least 80% correct (49 CFR 383.135 (eCFR))
Number of questions Varies by state. Check the CDL manual from your state’s licensing agency.
Our practice test 25 questions per attempt, drawn at random from 45. Pass mark: 80%.

Topics covered

  • Air brake system parts 20 questions
  • Using air brakes 13 questions
  • Inspecting air brakes 9 questions
  • Dual air brake systems 3 questions

Sample questions

A few questions from the set. Try to answer before opening each explanation.

  1. Sample question 1

    If you always drive a straight truck or combination with working ABS on all axles, what may you do in an emergency stop?

    • AUse only the parking brake
    • BFully apply the brakes
    • CPump the brake pedal as fast as you can
    • DShift into neutral before braking
    Show answer

    Answer: B. The one exception to braking as you always have is a vehicle with working ABS on every axle, where full brake application is allowed in an emergency stop.

    Source: Commercial Driver's License Manual, Version 07/20/2026 (form DMV 60A), section 5.4.2 Braking with Antilock Brakes.

  2. Sample question 2

    During the engine compartment checks, what should you check on a belt-driven air compressor?

    • AThe cut-out pressure shown on the dash gauges
    • BThe thickness of the brake linings
    • CThe color of the compressor's air filter
    • DThe condition and tightness of the compressor drive belt
    Show answer

    Answer: D. When the compressor is driven by a belt, the engine compartment check includes making sure that belt is in good shape and properly tight.

    Source: Commercial Driver's License Manual, Version 07/20/2026 (form DMV 60A), section 5.3.1 During Step 2 Engine Compartment Checks.

  3. Sample question 3

    During the final air brake check, how do you lower tank pressure to see whether the compressor cuts in?

    • ARun the engine at a fast idle
    • BWith the engine idling, step on and off the brake
    • CRev the engine several times in neutral
    • DWait with the engine idling and the brakes off
    Show answer

    Answer: B. Pressing and releasing the brake pedal uses up air, so the gauge falls until the governor should let the compressor start pumping again.

    Source: Commercial Driver's License Manual, Version 07/20/2026 (form DMV 60A), section 5.3.3 Step 7 Final Air Brake Check.

  4. Sample question 4

    What can happen if you press and release the brake pedal when there is no need to?

    • AAir can be let out faster than the compressor can replace it
    • BThe governor raises the cut-out pressure
    • CThe spring brakes release by themselves
    • DThe brake linings cool down faster
    Show answer

    Answer: A. Every release of the pedal lets some compressed air escape, so needless pumping can drain the tanks faster than the compressor refills them, and the brakes stop working if pressure gets too low.

    Source: Commercial Driver's License Manual, Version 07/20/2026 (form DMV 60A), section 5.1.7 The Brake Pedal.

  5. Sample question 5

    In stab braking, after you release the brakes, how long can it take for the wheels to start rolling?

    • AUp to five seconds
    • BUp to ten seconds
    • CUp to one second
    • DUp to thirty seconds
    Show answer

    Answer: C. The wheels may need as long as a second to roll again, and reapplying the brakes before they do will keep the vehicle from straightening out.

    Source: Commercial Driver's License Manual, Version 07/20/2026 (form DMV 60A), section 5.4.3 Emergency Stops.

How to prepare

  • Read the matching sections of your state’s CDL manual before you practice.
  • Use practice mode first: it shows the explanation and the manual reference after each answer.
  • For every missed question, reread the whole manual section we cite.
  • Switch to exam mode when you score well above 80% without help.

More detail in our guide How to Study for the CDL Knowledge Tests.

Other CDL practice tests

Which tests you need depends on your license class and endorsements, as explained in CDL Classes, Endorsements and Restrictions Explained.

Frequently asked questions

What score do I need to pass?

Federal rules require at least 80% correct on each CDL knowledge test (49 CFR 383.135 (eCFR)).

Are these the questions on the real test?

No. Real test questions are not public. We write our own questions from the official manual, so they cover the same material but are not copies of test questions.

Is the CDL manual the same in every state?

State CDL manuals are built on the same national model manual from AAMVA, so the knowledge content is largely the same. We compared 3 state editions for this test: 45 of 45 quotes appear word for word in the same section of all of them. Your own state’s manual is the final word if anything differs.

How do you check the answers?

Each question stores the manual section (or page) and an exact quote that a script checks against the manual text, then an independent AI review answers it from that part of the manual alone. See our editorial policy. Found a mistake? Tell us.

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25 questions, pass mark 80%. Free, no sign-up.

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Sources

Questions cite the newest edition we have. We also check every quote against the other state editions of the same model manual, section by section.