CDL Air Brakes practice test

Take it if you will drive a vehicle with air brakes. Without it, your license carries an air-brake restriction.

Examlane has 164 Air Brakes questions in 5 chapters. The usual test has 25 questions and needs 80% to pass. Some states set a different length: see the state table.

Chapters

Chapter pages: Air brake system parts, Inspecting air brakes.

Ten free questions

Open a question to see the answer and why.

1. 1. What is used to operate an air brake system?

   1. Hydraulic fluid pressure
   2. Compressed air
   3. Engine vacuum
   4. Electric motors

   Answer: B. Compressed air

   Air brakes work by using compressed air to apply the brakes.

   Based on: CDL manual, Section 5.0 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

2. 2. What is the job of the air compressor in an air brake system?

   1. It controls when pumping starts and stops
   2. It pumps air into the air storage tanks
   3. It drains water and oil from the tanks
   4. It opens to release too much pressure

   Answer: B. It pumps air into the air storage tanks

   The compressor is the part that pumps air into the storage tanks (reservoirs).

   Based on: CDL manual, Section 5.1.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

3. 3. What is a dual air brake system?

   1. One air system with two sets of brake controls
   2. Two air systems that each have their own brake pedal
   3. Two air systems that share one set of tanks and lines
   4. Two separate air systems that use one set of brake controls

   Answer: D. Two separate air systems that use one set of brake controls

   A dual system has two separate air systems, each with its own tanks, hoses and lines, worked by one set of controls.

   Based on: CDL manual, Section 5.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

4. 4. A vehicle with air brakes is checked using the basic inspection procedure plus extra air brake items. How many steps does that basic procedure have?

   1. Seven
   2. Five
   3. Six
   4. Eleven

   Answer: A. Seven

   Air brake vehicles are inspected with the same basic seven-step procedure, with extra air brake checks added.

   Based on: CDL manual, Section 5.3 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

5. 5. You are making a normal stop in a truck with a manual transmission. When should you push the clutch in?

   1. As soon as you touch the brake pedal
   2. When engine speed has fallen to near idle
   3. As soon as you let off the accelerator
   4. When the brake pedal is halfway down

   Answer: B. When engine speed has fallen to near idle

   Keep the clutch engaged until engine rpm has dropped close to idle, then push it in to finish the stop.

   Based on: CDL manual, Section 5.4.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

6. 6. Which three braking systems make up air brakes?

   1. Front, rear and trailer brakes
   2. Service, parking and emergency brakes
   3. Service, engine and exhaust brakes
   4. Disc, drum and wedge brakes

   Answer: B. Service, parking and emergency brakes

   Air brakes are really three braking systems: the service brake, the parking brake and the emergency brake.

   Based on: CDL manual, Section 5.0 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

7. 7. Your air compressor has its own oil supply. What should you do before you drive?

   1. Drain the oil and refill it
   2. Disconnect the v-belt
   3. Set the governor to cut-out
   4. Check the oil level

   Answer: D. Check the oil level

   A compressor with its own oil supply needs its oil level checked before you drive.

   Based on: CDL manual, Section 5.1.1 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

8. 8. In a typical dual air brake system, one system handles the regular brakes at the front axle. What does the other system handle?

   1. The regular brakes for the rear axle or axles
   2. Only the brakes on the trailer and the dolly behind it
   3. Only the parking brakes and the emergency brakes
   4. Only the engine brake

   Answer: A. The regular brakes for the rear axle or axles

   The two systems split the regular brakes between them, with one system working the rear axle or axles.

   Based on: CDL manual, Section 5.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

9. 9. If an air compressor is belt-driven, what should you check about the belt?

   1. Its width and weight
   2. Its brand and installation date
   3. Its condition and tightness
   4. Its length and color

   Answer: C. Its condition and tightness

   A belt-driven compressor needs a belt that is in good condition and properly tight.

   Based on: CDL manual, Section 5.3.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

10. 10. What does an antilock braking system do when its computer senses that a wheel is about to lock up?

    1. It reduces braking pressure to a safe level
    2. It applies the spring brakes
    3. It raises pressure so you stop sooner
    4. It releases all the air from the tanks

    Answer: A. It reduces braking pressure to a safe level

    ABS lowers the braking pressure to a safe level when lockup is about to happen, so you keep control of the vehicle.

    Based on: CDL manual, Section 5.4.2 (Georgia edition of the national model manual, read 2026-10-24). Question in our own words.

This is practice for the knowledge test. It is not Entry-Level Driver Training and does not count toward any federal training requirement.