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 Alaska Commercial Driver 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
13. 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.
14. Once the air tanks are at an air pressure level of 125 psi, the air compressor governor will:
Explanation
An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level around 125 psi. This air pressure level is referred to as the "cut-out" level.
15. Lights that indicate that anti-lock brakes are not working are:
Explanation
Vehicles equipped with Anti-Lock Braking Systems (ABS) have yellow malfunction lights to indicate issues in the braking system.
16. If the safety relief valve in the air brake system releases air:
Explanation
An air brake system has a safety relief valve, which releases air from the tanks if the pressure gets too high. If the valve must operate, something in the system is wrong and should be addressed by a mechanic.
17. What color malfunction lamps do vehicles equipped with ABS have?
Explanation
Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.
18. What kind of brakes do most newer heavy-duty trucks use?
Explanation
