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 Maryland Commercial Driver Guide. 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 an Anti-Lock Braking System (ABS):

Is required in some states.

Shortens brake response time.

Provides additional control.

An Anti-Lock Braking System (ABS) helps to provide additional control during hard braking, but does not necessarily shorten a vehicle's stopping distance.

20. If the brake pads rub against the brake drums and create too much heat:

The brakes will stick.

The brakes will become extra sensitive.

The brakes may stop working.

The air compressor will kick on to cool the brakes.

Brakes heat up with use. If they are overused and become too hot, expansion and chemical changes will make them less effective and eventually cause them to stop working altogether. This is known as "brake fade."

21. 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.

22. What do the two systems of a dual air brake system share?

Hoses

An air compressor

Air tanks

Both systems in a dual air brake systems share a single air compressor. If the air compressor is damaged, neither system will be able to operate properly.

23. Air brakes use ____ to function.

Compressed air

Liquid nitrogen

Carbon dioxide

The brakes in an air brake system use compressed air to function properly.

24. You should not use the parking brake:

If your vehicle is stopped on a level surface.

If your vehicle is stopped on a slight incline.

If your vehicle's brakes are very hot.

If your vehicle's other braking systems seem to be working adequately.

A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.

25. To use the stab braking method, you should:

Apply the brakes completely until the wheels lock up, release the brakes until the wheels start rolling, then repeat the process.

Apply the brakes about halfway, but allow the wheels to keep rolling.

Apply the brakes completely until the wheels lock up and the vehicle stops.

Apply the emergency brake until the vehicle starts to slow.

The stab braking method for emergency stops involves fully applying the brakes until they lock up. The brakes are then released until the wheels start rolling, and then the process is repeated.

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