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 Iowa 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 25

Passing Score 20

19. A wig wag is:

A low pressure warning device.

A tube that carries air to the brakes.

A type of air brake system.

Vehicles with air brakes are required to be equipped with a low pressure warning device. A wig wag is a type of low air pressure warning device. This device drops a mechanical arm into the driver's view if the pressure in the tanks drops to a level between 55 and 75 psi.

20. When traveling down a steep downgrade:

The air brakes should be used.

The vehicle should be placed in a low gear and the driver should use engine braking.

The driver should continually downshift instead of using the brakes.

On long and/or steep downgrades, you should primarily use engine braking to control the speed of your vehicle. Use your brakes only as a supplement to this effect.

21. Air storage tanks:

Are not allowed on a vehicle.

Hold compressed air for the brakes.

Should be drained of excess air after every trip.

In an air brake system, the air storage tanks hold compressed air to be used by the brakes. The number and size of air tanks varies among vehicles.

22. What tells you how much pressure is in your vehicle's air tanks?

The supply pressure gauge

The ABS malfunction lamp

The tractor protection valve

A vehicle that is equipped with air brakes must also be equipped with a supply pressure gauge. This gauge tells the driver how much air pressure is in each of the vehicle's air tanks.

23. If the low air pressure warning signal comes on, you should:

Continue driving, but have the brakes repaired within a week.

Pull over and inspect the brakes.

Phone a mechanic while driving.

If the low air pressure warning signal comes on while you are driving a vehicle with air brakes, you should immediately bring the vehicle to a safe stop while you are still able to control the brakes. Inspect and repair the brakes as soon as possible.

24. What color light indicates a vehicle's ABS is not working?

Green

Blue

Yellow

On vehicles with Anti-Lock Braking Systems (ABS), yellow malfunction lamps alert the driver to ABS malfunction.

25. An application pressure gauge shows:

How much air pressure is being applied to the brakes.

How much air pressure is available.

How much air pressure is required to stop a vehicle.

If a vehicle is equipped, an application pressure gauge shows how much air pressure is being applied to the brakes. This gauge can help a driver identify if their brakes are beginning to fade.

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