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 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

1. How many air storage tanks are used in an air brake system?

Explanation
Air storage tanks are used to hold compressed air. The number and size of air tanks in an air brake system varies among vehicles.

2. Most heavy-duty vehicles use ____ air brake systems.

Explanation
The majority of heavy-duty vehicles are equipped with dual air brake systems.

3. All air tanks must include:

Explanation
Air brake system tanks must contain drain valves. These valves are used to drain accumulated oil and water from the tanks and may be either manually or automatically operated.

4. 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. On vehicles with hydraulic brakes, the brakes work instantly when the pedal is pressed.

5. Most heavy-duty vehicles use:

Explanation
Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.

6. To stop a vehicle using air brakes:

Explanation
To stop normally in a vehicle with air brakes, press down the brake pedal.
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