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 or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the North 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. If the low pressure warning light comes on while you are driving:

Braking will only occur if there is enough air in the tanks.

You can brake 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 continue driving, but turn the emergency flashers on to warn other motorists.

If the low air pressure warning light turns on, you should stop and safely park your vehicle as soon as possible. Controlled braking will be possible only as long as enough air remains in the tanks.

20. A dual air brake system:

Has a single air brake system, but uses two sets of controls.

Has one air brake system for each side of the truck.

Has two brakes for each wheel.

Has two separate air brake systems, but uses a single set of controls.

A dual air brake system has two separate air brake systems that use a single set of brake controls. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle.

21. In a dual air brake system, a leak in one system:

Always means there are leaks in both systems.

May not affect the other system.

Is not something to worry about.

Will also affect the other system.

A dual air brake system is made up of two separate air brake systems. If there is an air leak in one system, it may not affect the other.

22. Front brake limiting valves were intended to:

Prevent the front tires from skidding.

Prevent the front tires from overheating.

Create equal brake usage.

Remove uncertainty when applying the brakes.

Some older vehicles with air brakes have front brake limiting valves. These valves were intended to reduce the risk of front wheels skidding. However, research has shown that such devices are unnecessary, so they should be left in the "normal" position.

23. When operating a vehicle with a dual brake system, a driver should:

Let the vehicle warm up before driving to ensure that fuel reaches the engine.

Wait to begin driving until the air compressor builds up a minimum pressure of 100 psi in both the primary and secondary systems.

Begin driving just after the vehicle starts.

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

Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum pressure of 100 psi in both the primary and secondary systems.

24. The air pressure in a dual air brake system should build from 85 to 100 psi within:

Two minutes.

15 seconds.

10 minutes.

45 seconds.

When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

25. When leaving a vehicle unattended, a driver should:

Always set the parking brake.

Only set the parking brake if the vehicle is parked on a slope.

Deflate the tires by 10 percent.

Always apply the parking brake when leaving your vehicle unattended.

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