- Updated for March 2025
- Based on 2025 NC commercial driver's license manual
Free North Carolina CDL Air Brakes Test 2025
If you fail to pass the North Carolina DMV CDL Air Brakes Knowledge Test, your CDL will include the “L” restriction, preventing you from operating heavy commercial motor vehicles (CMVs) with air brakes. This restriction will negatively affect your job prospects in commercial driving. Failing the air brakes test in North Carolina also results in a one-day waiting period and a fee should you decide to retake the test. Our North Carolina DMV CDL Air Brakes Practice Tests are the perfect tool for passing your knowledge exam on the first attempt.
Navigating North Carolina’s diverse terrain, from the coastal plains in the east to the Appalachian Mountains in the west, requires careful handling on steep grades and sharp curves, making reliable braking systems essential. Additionally, North Carolina experiences strong thunderstorms, winter snow, and ice, compounding the need for air brake-qualified drivers. Key transportation routes in North Carolina include I-40 (an east-west corridor connecting Wilmington to the western mountains), I-85 (a north-south route linking North Carolina and Georgia), I-95 (a north-south route along the East Coast), and US-64 (connecting the western and eastern parts of the state). Most semi-trucks, tractor-trailers, and commercial buses rely on air brakes for safe travel; therefore, removing the air brake restriction from your CDL is vital for expanded job opportunities.
The Tar Heel State’s economy depends on air brake-qualified drivers in key industries, including agriculture (tobacco, poultry, and sweet potatoes), manufacturing (furniture and textiles), and logistics. Companies requiring the air brake qualification include Tyson Foods and Smithfield Foods in the agriculture industry and Volvo Trucks (Greensboro) and Carolina Biological Supply in the manufacturing sector. FedEx Freight and XPO Logistics in the logistics and freight industry and Duke Energy in the energy sector rely on air brake-qualified drivers. Major charter bus companies, including Greyhound Lines and Carolina Trailways, rely on air brake-equipped vehicles. Additionally, the {state-name) school districts use air brake-equipped full-size school buses. The “L” restriction makes these jobs unattainable.
The written Air Brakes knowledge test features multiple-choice questions based on the state’s CDL manual (North Carolina CDL Handbook 2025) and requires a minimum passing score of 80%. With our practice tests, you’ll learn faster with instant feedback on all your responses, ensuring you pass the knowledge test.
Our CDL Air Brakes Practice Tests cover everything you’ll need and mimic the official DMV Air Brakes Knowledge Test.
- Perfect for first-time and renewal CDL/CLP applicants, and those adding endorsements
- Triple-checked for accuracy
What you need to know
What to expect on the actual NC DMV exam
questions
correct answers to pass
passing score
List of questions (classic view)
- Under which conditions are front wheel brakes good?
- When should you use the parking brake?
- The purpose of a supply pressure gauge is
- What is the best way to test your vehicle's low air pressure warning signal?
- The tractor protection valve
- How can you tell if your vehicle is equipped with an antilock braking system (ABS)?
- Which of the following should you do before leaving your vehicle unattended?
- How would you check your truck's slack adjusters?
- Slack adjusters are
- Which of the following is NOT part of the air brake system?
- Which of the following will be true about your brake function if your antilock braking system (ABS) fails?
- At what measurement is the safety valve USUALLY set to open?
- An antilock braking system (ABS)
- Which of the following can cause brakes to fade or fail?
- Which of the following are true about a dual air brake system?
- Which of the following is NOT part of the braking process when you're driving a tractor-trailer combination vehicle with an antilock braking system (ABS)?
- When should you drain your air tanks?
- After the initial drop, the maximum acceptable leakage rates per minute are
- What is the best way to test if your vehicle's spring brakes come on automatically?
- Spring brakes are
- How do brakes work on a long, steep downgrade?
- Which of the following is NOT part of the drum brake?
- If the air tanks are not drained,
- Which vehicles must have low air pressure warning signals?
- Why must you pass a knowledge test on air brakes?
- The low air pressure warning signal will come on before the pressure in the air tanks falls below
- A low pressure warning signal is required on
- All vehicles equipped with air brakes have
- With air brake-equipped vehicles, the parking brakes should be used
- The use of air brakes on a downgrade is only a supplement to the
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