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 Idaho Commercial Driver’s License 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
7. What should happen before the air pressure in an air brake system tank falls below 55 psi?
Explanation
The low air pressure warning signal must activate before the air supply pressure drops below 55 psi in the air tank. If the warning signal does not turn on when being tested during an inspection, the vehicle is not safe to drive.
8. Why do large vehicles use air brakes?
Explanation
Air brakes are an effective and safe way of stopping large and heavy vehicles, as long as they are maintained and used properly.
9. Failing to drain air tanks could result in:
Explanation
In an air brake system, the air tanks must be periodically drained to remove accumulations of water and compressor oil. If water is not removed, it could freeze in cold weather and cause brake failure.
10. ____ make up the emergency brake system.
Explanation
In an air brake system, there are three different braking systems: a service brake system, a parking brake system, and an emergency brake system. The emergency brake system uses parts of both the parking and service brake systems.
11. Foundation brakes are used:
Explanation
Foundation brakes are used at each wheel. The most common type is the S-cam drum brake.
12. Using an Anti-Lock Braking System (ABS):
Explanation
