Virginia CDL Air Brake Test (VA) 2026

4.9 out of 5 (102 votes)
80% Passing score
20 Questions
4 Mistakes allowed
As you prepare for your commercial driver's license in Virginia, it's crucial to have a thorough understanding of air brake systems. Our Virginia DMV practice test is designed to help you master the essential components and principles of air brakes, ensuring you are well-prepared for the actual test. This DMV permit practice test consists of 20 multiple-choice questions, carefully crafted to cover every aspect of air brake systems. You'll delve into the mechanics of compressors, reservoirs, and brake chambers, gaining a deep understanding of how these components work together to ensure safe and efficient braking. The VA CDL air brake practice test also includes questions on operational principles, helping you understand the procedures and protocols that are vital for maintaining and using air brakes effectively. Additionally, you'll encounter questions about brake lag time, a unique characteristic of air brakes that affects stopping distances and requires careful calculation by drivers. To pass this Virginia DMV learners permit practice test, you'll need to correctly answer at least 16 questions. This passing score is designed to ensure that you have a comprehensive grasp of the material, equipping you with the knowledge needed to safely operate commercial vehicles equipped with air brakes. Our DMV permit practice test is not only a valuable study tool but also an effective way to familiarize yourself with the test format. It mirrors the multiple-choice and true or false format used in the actual DMV test, helping you develop the skills to eliminate incorrect answers and identify the correct ones. Upon completing the Virginia CDL air brakes practice test, you'll have the opportunity to review your answers and examine hints and explanations for any questions you missed, enhancing your understanding of the material. We take pride in keeping our VA DMV permit test practice up-to-date with the latest driving laws and regulations. This ensures that you're studying the most current information, giving you the best possible preparation for your CDL air brake endorsement. Our practice test is updated for 2026, reflecting the latest standards and requirements for commercial drivers in Virginia. Prepare effectively and gain confidence in your air brake knowledge with our comprehensive Virginia CDL air brake test. Master the fundamentals of air brake operation and ensure your readiness for the DMV test.
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Sample Virginia Air Brakes Test Questions

Question 1

In an S-cam air brake, what does the slack adjuster help do?

  1. A. Regulate pressure inside the air reservoirs
  2. B. Release the spring brakes when the vehicle is parked
  3. C. Change the amount of free play in the brake pedal
  4. D. Transfer pushrod movement into rotation of the brake camshaft

Correct answer: D. – Transfer pushrod movement into rotation of the brake camshaft

Air pressure moves the brake chamber pushrod, which moves the slack adjuster and turns the brake camshaft. The rotating S-cam forces the brake shoes against the drum. During inspection, movement exceeding about one inch where the pushrod attaches indicates that the brake probably needs adjustment or has another mechanical problem.

Source: Virginia Commercial Driver’s License Manual — §§ 5.1.8, “Foundation Brakes,” and 5.3.2, “During Step 5 Walk-around Inspection”

Question 2

Under good conditions, an air-brake vehicle traveling at 55 mph has a total stopping distance of about 100 feet.

  1. A. TRUE
  2. B. FALSE

Correct answer: B. – FALSE

The statement is false. Virginia’s air-brake section explains that an average driver traveling at 55 mph under good traction and brake conditions needs more than 450 feet to stop. Air-brake lag alone adds approximately 32 feet to the total distance.

Source: Virginia Commercial Driver’s License Manual — § 5.4.4, “Stopping Distance”

Question 3

Why must you select a proper low gear before descending a long, steep grade?

  1. A. Engine braking should provide the principal speed control, with service brakes used as a supplement
  2. B. A low gear eliminates every need to use the service brakes
  3. C. It keeps the transmission cooler by removing engine braking
  4. D. It increases the air compressor’s governor cut-out pressure

Correct answer: A. – Engine braking should provide the principal speed control, with service brakes used as a supplement

Engine braking should be the principal method of controlling speed on a long, steep downgrade. The service brakes supplement that effect and remain available for necessary slowing or stopping. Select the low gear before descending because speed buildup may make a later downshift impossible and eliminate the engine-braking benefit.

Source: Virginia Commercial Driver’s License Manual — §§ 2.16.2, “Select the Right Gear before Starting Down the Grade,” and 2.16.4, “Proper Braking Technique”

Question 4

A safety relief valve is installed in the first tank supplied by the air compressor to protect the air-brake system from excessive pressure.

  1. A. TRUE
  2. B. FALSE

Correct answer: A. – TRUE

The statement is true. The safety relief valve is installed in the first tank to which the compressor sends air. It protects that tank and the remainder of the system from excessive pressure and is usually set to open at approximately 150 psi.

Source: Virginia Commercial Driver’s License Manual — § 5.1.6, “Safety Valve”

Question 5

If the low-air-pressure warning activates while driving, you should stop and safely park as soon as possible.

  1. A. TRUE
  2. B. FALSE

Correct answer: A. – TRUE

The statement is true. A low-air warning may indicate a leak or another loss of system pressure, and braking ability can become limited. Stop and safely park while the service brakes can still be controlled; spring brakes may apply automatically when pressure falls into roughly the 20-to-45-psi range.

Source: Virginia Commercial Driver’s License Manual — §§ 5.1.14, “Spring Brakes,” and 5.4.7, “Low Air Pressure”

Question 6

Which procedure is used to test the low-air-pressure warning signal?

  1. A. Shut off the engine, turn on electrical power, and repeatedly press and release the brake pedal
  2. B. Run the engine at high idle while holding the brake pedal down continuously
  3. C. Pull hard on each slack adjuster while the parking brakes remain applied
  4. D. Drive at least 20 mph and make a sudden emergency stop

Correct answer: A. – Shut off the engine, turn on electrical power, and repeatedly press and release the brake pedal

With sufficient initial air pressure, shut off the engine and turn on the electrical power. Repeatedly press and release the brake pedal to reduce reservoir pressure. Under Virginia’s current manual, the warning must activate before pressure in the lowest tank drops below 55 psi; a warning that does not operate must be repaired.

Source: Virginia Commercial Driver’s License Manual — § 5.3.3, “Step 7 Final Air Brake Check” — “Test Low Pressure Warning Signal”

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