New Hampshire CDL Air Brake Test (NH) 2026

5 out of 5 (47 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Welcome to the ultimate resource for your New Hampshire CDL air brake test preparation. This practice tool is specifically designed to provide you with an in-depth understanding of air brake systems, critical for all aspiring commercial drivers in the state. Our NH DMV practice test consists of 20 multiple-choice questions, meticulously curated to cover every essential aspect of air brake systems. You'll delve into topics like compressors, reservoirs, and brake chambers while also grasping operational principles and vital safety protocols. One standout feature of our CDL air brakes practice test is its focus on the unique brake lag time inherent in air brake systems. This aspect is crucial for drivers, as it impacts stopping distances significantly. Understanding this concept is vital to ensuring safety on the road, and our New Hampshire permit practice test provides the ideal opportunity to master it. With no time constraints, you can take all the time you need to thoughtfully engage with each question, enabling a thorough grasp of the material. Upon completion of the NH drivers test practice, you can review your answers, including explanations and hints for any questions you missed. This feature ensures you fully understand the concepts and allows for learning from mistakes. Although real DMV questions cannot be published, our DMV written test practice closely mirrors the actual test format and phrasing, offering you an authentic and valuable practice experience. Achieving a passing score of 16 or more correct answers will signify your readiness for the real DMV air brake test. This driving test practice is your key to mastering the fundamentals of air brake operation and securing your air brake endorsement. Prepare with confidence and gain the essential knowledge needed for safe, effective driving.
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Sample New Hampshire Air Brakes Test Questions

Question 1

With the engine off and parking brake released, which air-loss rate is acceptable for a fully charged single vehicle?

  1. A Less than 1 psi in one minute
  2. B Less than 2 psi in one minute
  3. C Less than 3 psi in one minute
  4. D Less than 4 psi in one minute

Correct answer: B – Less than 2 psi in one minute

For this leakage test, fully charge the air system, turn off the engine, release the parking brake, and time the pressure drop. The loss rate should be less than 2 psi in one minute for a single vehicle. For a combination vehicle, the corresponding rate should be less than 3 psi in one minute.

Source: New Hampshire Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 2

What function do spring brakes normally serve in an air-brake vehicle?

  1. A They operate the hydraulic brake circuit
  2. B They supply compressed air to the service brakes
  3. C They provide parking and emergency braking
  4. D They control only the trailer service brakes

Correct answer: C – They provide parking and emergency braking

Spring brakes are commonly used to meet parking- and emergency-brake needs. During normal driving, air pressure holds the powerful springs back. Releasing that air through the parking-brake control—or losing air because of a system leak—allows the springs to apply the brakes mechanically.

Source: New Hampshire Commercial Driver License Manual — § 5.1.14, “Spring Brakes”

Question 3

What is the purpose of an alcohol evaporator in an air-brake system?

  1. A To reduce the risk of ice forming in air valves and other parts during cold weather
  2. B To increase air-tank pressure above the governor cutout level
  3. C To eliminate the need to drain manually operated air tanks
  4. D To remove alcohol that has condensed inside the tanks

Correct answer: A – To reduce the risk of ice forming in air valves and other parts during cold weather

An alcohol evaporator introduces alcohol into the air system to reduce the risk of ice forming in valves and other components during cold weather. Ice can interfere with brake operation. The alcohol container should be checked daily in cold weather, and air tanks still require daily drainage unless automatic drain valves are installed.

Source: New Hampshire Commercial Driver License Manual — § 5.1.5, “Alcohol Evaporator”

Question 4

Which part of an air-brake system applies and releases the brakes when the driver operates the brake pedal during normal driving?

  1. A Parking brake system
  2. B Service brake system
  3. C Emergency brake system
  4. D Air-storage system

Correct answer: B – Service brake system

The service brake system applies and releases the brakes when the driver uses the brake pedal during normal operation. Pressing the pedal increases the air pressure applied to the brakes, while releasing it reduces that pressure. The parking and emergency systems perform different functions.

Source: New Hampshire Commercial Driver License Manual — § 5, “Air Brakes” and § 5.1.7, “The Brake Pedal”

Question 5

During an applied air-leakage test, how much pressure may a single vehicle lose with the engine off and the service brake fully applied?

  1. A No more than 3 psi in one minute
  2. B No more than 2 psi in 45 seconds
  3. C No more than 1 psi in one minute
  4. D No more than 1 psi in 30 seconds

Correct answer: A – No more than 3 psi in one minute

Build air pressure to governor cutoff, turn off the engine, release the parking brake, and fully apply the foot brake for one minute. A single vehicle must not lose more than 3 psi during that minute. A pressure loss greater than 3 psi indicates excessive leakage that must be repaired before driving.

Source: New Hampshire Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 6

What information is displayed by an air-supply pressure gauge?

  1. A The pressure currently being applied to the brake chambers
  2. B The air pressure available in the storage tanks
  3. C The total amount of air used during the trip
  4. D All of the above

Correct answer: B – The air pressure available in the storage tanks

The supply pressure gauge shows how much pressure is available in the air tanks. A dual air-brake system has a gauge for each half of the system or one gauge with two needles. Do not confuse it with an application pressure gauge, which displays the pressure being applied to the brakes.

Source: New Hampshire Commercial Driver License Manual — § 5.1.9, “Supply Pressure Gauges” and § 5.1.10, “Application Pressure Gauge”

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