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 two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Carolina 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 vehicle equipped with an Anti-Lock Braking System (ABS) uses a ____ light to warn that the system is not working properly.

Green

Yellow

Orange

White

Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.

20. When traveling down a steep downgrade, the best way to use your brakes is to:

Ride the brakes all the way down the hill.

Apply the brakes for a few seconds, then release the brakes for a few seconds. Continue to repeat these steps as you travel down the hill.

Apply the brakes only near the bottom of the downgrade.

Apply consistent pressure to the brake pedal all the way down the hill.

On a long or steep downgrade, brakes should only be used to supplement the braking effect of the engine. Apply the brakes just enough to feel a definite slowing down, then release them once you are about 5 mph below your target "safe" speed. Once your vehicle reaches its safe speed again, repeat this process.

21. When the spring brakes are on, you should never:

Turn on the lights.

Turn off the vehicle.

Push down the brake pedal.

Never push down the brake pedal while the spring brakes are activated. The combined force of springs and air pressure could damage the brakes.

22. When about to drive a vehicle with a dual brake system, a driver should:

Let the vehicle warm up to ensure the fuel reaches the engine.

Wait for air pressure to build in both the primary and secondary systems.

Begin driving just after the engine starts.

Pump the pedal about 20 times to build pressure, then begin driving.

Before driving a vehicle with a dual air brake system, allow time for the compressor to build up pressure to at least 100 psi in both systems.

23. The two markings on a front brake limiting valve usually read:

"Normal" and "slippery."

"Low" and "high."

"Left" and "right."

Some vehicles with air brake systems manufactured before 1975 have a front brake limiting valve with "normal" and "slippery" settings.

24. In a newer vehicle, you apply the parking brake:

By using a diamond-shaped yellow knob.

By using a round red knob.

By using a square green knob.

By using a black round knob.

In a newer vehicle with air brakes, the parking brake is controlled by a diamond-shaped yellow knob. The knob is pulled out to apply the parking brakes and pushed in to release them.

25. If the low pressure warning light comes on while you are driving:

Braking will only be possible if there is still enough air in the tanks.

You can apply the brakes 14 times before the air in the system runs out.

You should continue to drive normally and check the brake system when it is convenient.

You should stay at least 100 feet away from other vehicles.

When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

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