Instructions

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 25

Passing Score 20

7. The ____ are activated by an electric switch that is triggered by the brake pedal.

Headlights

Turn signals

Brake lights

In a vehicle with air brakes, the brake lights are activated when the brake pedal is pushed and air pressure moves an electric switch. With the application of air pressure, the switch will then turn on the brake lights.

8. If you are braking on dry pavement while traveling at 55 mph, how much distance will brake lag add to your overall stopping distance?

32 feet

45 feet

20 feet

The total stopping distance for vehicles equipped with air brakes is made up of four factors: perception distance, reaction distance, brake lag distance, and braking distance. When braking at a speed of 55 mph while driving on dry pavement, the brake lag can add around 32 feet to the vehicle's total stopping distance.

9. In a dual air brake system:

Each system has separate air tanks, hoses, and lines.

The systems share air tanks, but each has its own separate hoses and lines.

Each system uses the same lines and hoses.

One system is the main braking system and a second system is ready to be used if the first one fails.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines.

10. Air tank drains:

Allow rain water to enter an air tank.

Are used to drain water and oil from an air tank.

Should never be opened.

Must remain open during driving.

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Manually operated air tank drains must be opened daily to remove this build-up.

11. Using the brakes creates heat. If too much heat is produced:

The brakes may not work.

The brakes may squeak more than usual.

The brakes will brake unevenly.

Brakes are designed to take a lot of heat, but drivers should not rely solely on the brakes to slow their vehicle. Brakes may fade and lose their ability to slow down the vehicle if they become too hot, so drivers should also rely on the engine braking effect.

12. Some air brake systems introduce alcohol into the system to:

Make the brakes work without squeaking.

Prevent ice from forming in the brake system.

Prevent people from breathing the air from the system.

Some air brake systems contain an alcohol evaporator. An evaporator introduces alcohol into the system to help inhibit the formation of ice in cold weather.

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