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 l. 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. 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.

20. An alcohol evaporator in an air brake system:

Makes the brakes work without squeaking.

Prevents ice from forming in the braking system.

Lubricates parts of the braking system.

Some air brake systems include an evaporator that introduces alcohol into the system. The alcohol can help prevent ice from forming within the system.

21. The leakage rate for a single vehicle with air brakes should be no more than ____ in one minute during a static leakage test.

1 psi

2 psi

3 psi

When performing a static leakage test on a single vehicle with air brakes, the leakage rate should be no more than 2 psi in a minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

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

Higher

Faster

Lower

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

23. Air pressure should build up in a single air system within:

15 minutes.

12 minutes.

Three minutes.

In single air systems, air pressure should build from approximately 50 to 90 psi within three minutes.

24. Having ABS on only one axle:

Can be dangerous.

Still allows you additional control when braking.

Slows the vehicle, but cannot stop it.

If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer, or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.

25. Before driving a vehicle with air brakes, you should ensure that the ____ come on automatically when air pressure falls below 45 psi.

Spring brakes

Parking brakes

Air brakes

Before driving a vehicle with air brakes, you should ensure that the spring brakes come on automatically when air tank pressure falls to a level between 20 and 45 psi. You can do this by chocking the wheels and releasing air from the braking system by stepping on and off the brake pedal. Once the pressure levels drop to an unsafe level, the parking brake valve should pop out and spring brakes should come on.

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