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 or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Commercial Driver Guide. 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. While operating on a downgrade, you should brake until you reach a speed that is:
Explanation
While driving downhill, you should hold down the brake pedal until your vehicle reaches a speed 5 mph below your safe speed, then release the brake pedal. Repeat this process.
2. A low air pressure warning signal should activate:
Explanation
In an air brake system, a low air pressure warning signal must come on if air pressure in the tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig wag.
3. If one air system in a dual air brake system is very low on pressure:
Explanation
In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.
4. Pressing and releasing a brake pedal unnecessarily can:
Explanation
In an air brake system, pressing and releasing the brake pedal unnecessarily can release air from the braking system faster than the compressor can replace it.
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 faster than the compressor can replace it, reducing the available air pressure. If the air pressure in an air brake system gets too low, the brakes will no longer work.
6. If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:
Explanation
