Air Brakes Knowledge Test CDL Practice Test
Practice with real Air Brakes exam questions and detailed explanations. Federally standardized — the same in all 50 states. Rated 4.8 stars by 1,000+ drivers.
Written by CDL holders and exam prep experts · Updated April 2026
Free Questions
10
Passing Score
80%
Time Limit
Typically 30 minutes; varies by testing location
Prerequisites
General Knowledge test must be completed first
What is the Air Brakes Knowledge Test Test?
The Air Brakes knowledge test is required for commercial vehicles equipped with air brake systems. Passing this test demonstrates your knowledge of air brake operation, inspection procedures, and safety protocols, and removes the 'L' restriction from your CDL.
Knowledge test to remove 'L' restriction (no air brakes) from CDL
Topic Breakdown
Air Brake System Components
~8 questions
- Compressor and reservoir systems
- Brake chambers and slack adjusters
- Air lines and fittings
Inspection and Testing
~7 questions
- Pre-trip inspection procedures
- Air pressure tests
- Brake adjustment checks
Safe Driving Practices
~6 questions
- Proper braking techniques
- Following distance requirements
- Downhill braking procedures
Emergency Procedures
~4 questions
- Air pressure loss procedures
- Emergency braking systems
- Brake failure protocols
Free Practice Questions
10 questionsQuestion 1 of 10
To check the free play of manual slack adjusters of S-cam brakes, you should park on:
Browse Air Brakes Questions
- 1. To check the free play of manual slack adjusters of S-cam brakes, you should park on:
- 2. A slack adjuster free play needs to be adjusted if it is more than about ____ when you pull hard on it.
- 3. Stab braking:
- 4. Which procedure is used in controlled braking?
- 5. Which braking technique may be used to stop quickly when you do not have ABS?
- 6. What is the purpose of the modulating control valve (when equipped)?
- 7. Some air brake systems have an alcohol evaporator. What may happen if you don't keep the proper level of alcohol?
- 8. The most common type of foundation brake found on heavy vehicles is the:
- 9. Which procedure is used for the spring brake test?
- 10. The air brake lag distance at 55 mph on dry pavement adds about ____ feet.
Study Tips
- 1Understand the air brake system components thoroughly
- 2Practice air pressure testing procedures
- 3Memorize safe following distances
- 4Know emergency braking procedures
- 5Review state air brake regulations and inspection requirements
CDL Requirements by State
The Air Brakes knowledge test is federally standardized, so the questions are the same nationwide. Age, renewal, and training rules vary by state — find yours below.
| State | Min Age (Intra / Inter) | Renewal | ELDT |
|---|---|---|---|
| California | 18 / 21 | 5 yrs | Required |
| Texas | 18 / 21 | 4 yrs | Required |
| Florida | 18 / 21 | 4 yrs | Required |
| New York | 18 / 21 | 8 yrs | Required |
| Pennsylvania | 18 / 21 | 4 yrs | Required |
| Illinois | 18 / 21 | 4 yrs | Required |
| Ohio | 18 / 21 | 4 yrs | Required |
| Georgia | 18 / 21 | 5 yrs | Required |
| Michigan | 18 / 21 | 4 yrs | Required |
| North Carolina | 18 / 21 | 5 yrs | Required |
| Alabama | 18 / 21 | 4 yrs | Required |
| Alaska | 18 / 21 | 5 yrs | Required |
| Arizona | 18 / 21 | 5 yrs | Required |
| Arkansas | 18 / 21 | 4 yrs | Required |
| Colorado | 18 / 21 | 5 yrs | Required |
| Connecticut | 18 / 21 | 4 yrs | Required |
| Delaware | 18 / 21 | 8 yrs | Required |
| Hawaii | 18 / 21 | 4 yrs | Required |
| Idaho | 18 / 21 | 4 yrs | Required |
| Indiana | 18 / 21 | 4 yrs | Required |
| Iowa | 18 / 21 | 5 yrs | Required |
| Kansas | 18 / 21 | 4 yrs | Required |
| Kentucky | 18 / 21 | 4 yrs | Required |
| Louisiana | 18 / 21 | 4 yrs | Required |
| Maine | 18 / 21 | 6 yrs | Required |
| Maryland | 18 / 21 | 8 yrs | Required |
| Massachusetts | 18 / 21 | 5 yrs | Required |
| Minnesota | 18 / 21 | 4 yrs | Required |
| Mississippi | 18 / 21 | 4 yrs | Required |
| Missouri | 18 / 21 | 6 yrs | Required |
| Montana | 18 / 21 | 4 yrs | Required |
| Nebraska | 18 / 21 | 5 yrs | Required |
| Nevada | 18 / 21 | 4 yrs | Required |
| New Hampshire | 18 / 21 | 5 yrs | Required |
| New Jersey | 18 / 21 | 4 yrs | Required |
| New Mexico | 18 / 21 | 4 yrs | Required |
| North Dakota | 18 / 21 | 5 yrs | Required |
| Oklahoma | 18 / 21 | 4 yrs | Required |
| Oregon | 18 / 21 | 8 yrs | Required |
| Rhode Island | 18 / 21 | 5 yrs | Required |
| South Carolina | 18 / 21 | 5 yrs | Required |
| South Dakota | 18 / 21 | 5 yrs | Required |
| Tennessee | 18 / 21 | 5 yrs | Required |
| Utah | 18 / 21 | 5 yrs | Required |
| Vermont | 18 / 21 | 4 yrs | Required |
| Virginia | 18 / 21 | 8 yrs | Required |
| Washington | 18 / 21 | 5 yrs | Required |
| West Virginia | 18 / 21 | 5 yrs | Required |
| Wisconsin | 18 / 21 | 4 yrs | Required |
| Wyoming | 18 / 21 | 4 yrs | Required |
Career Opportunities
Want the full background on this endorsement?
Read the complete Air Brakes Knowledge Test endorsement guide →Frequently Asked Questions
If you plan to drive a commercial vehicle equipped with air brakes, you must pass the air brakes knowledge test to remove the 'L' restriction from your CDL.
Air Brakes Study Resources
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