Air Brakes
This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Vermont Commercial Driver’s Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
Number of Question
Passing Score
1. A safety valve is set to open at ____ pounds per square inch (psi).
Explanation
The safety valve protects air tanks and the rest of an air brake system from accumulating too much air pressure. The safety valve is usually set to open at 150 psi.
2. Having ABS on only one axle:
Explanation
If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer, or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.
3. Air tank drains should:
Explanation
In an air brake system, air tank drains are used to remove water and compressor oil from the air tanks. When operating a drain, be sure to drain the tank completely.
4. What helps prevent wheel lockup when braking?
Explanation
The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.
5. What can happen if the air pressure gets too low in an air brake system?
Explanation
Pressing and releasing the brake pedal unnecessarily can let air out of the braking system faster than the compressor can replace it. Air brakes may cease to work effectively if the pressure becomes too low.
6. While operating on a downgrade, you should brake until you reach a speed that is:
Explanation
