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. 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.
2. In a dual air brake system, air pressure should build from 85 to 100 psi within ____ seconds.
Explanation
When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.
3. An alcohol evaporator is especially important:
Explanation
Some air brake systems contain an alcohol evaporator. This evaporator introduces alcohol into the system to help prevent ice from forming in cold weather.
4. Foundation brakes are used:
Explanation
Foundation brakes are used on each wheel of a CMV. The most common type of foundation brake is the s-cam drum brake.
5. Braking mechanisms are located inside:
Explanation
Drum brakes are attached to the wheels and located on the axles of a vehicle. The braking mechanisms that cause the vehicle to stop can be found inside of a drum brake.
6. Using an Anti-Lock Braking System (ABS):
Explanation
