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.. Read More

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 Kentucky 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

1. 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.

2. What is brake lag?

Explanation
Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

3. When you are about to start down a hill, you should switch into a ____ gear.

Explanation
Before starting down a hill, be sure to switch into a low gear. Gravity will increase your vehicle's speed as you travel downhill.

4. If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:

Explanation
If the low air pressure warning signal comes on while you are operating a vehicle with air brakes, you should stop and safely park the vehicle as soon as possible. It is essential that you are able to stop safely while you still have some braking power remaining.

5. To make a stop in a vehicle equipped with air brakes, the driver should:

Explanation
To make a normal stop in a vehicle that is equipped with air brakes, you should simply press the brake pedal down.

6. In a dual air brake system:

Explanation
There are two air brake systems in a dual air brake system. The systems share a set of brake controls, but each system has its own tanks, hoses, and lines.
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