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 four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Washington D.C. 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

7. Emergency brakes:

Are not required on trucks.

Are only required on trailers.

Are required on tractors.

Are optional.

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force.

8. To confirm that a trailer has ABS, you can:

Look under the trailer for wheel speed sensors coming from the back of the brakes.

Look under the hood for the ABS sticker.

Look at the tires.

Remove a tire and look for the ABS sensor on the axle.

If you are unsure if a trailer is equipped with an Anti-Lock Braking System (ABS), look under the vehicle for the electronic control unit and wheel speed sensor wires coming from the back of the brakes.

9. An air compressor governor will stop the compressor from pumping air once the air tanks have an air pressure level of:

125 psi.

100 psi.

150 psi.

80 psi.

An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level of 125 psi. This air pressure level is referred to as the "cut-out" level.

10. Air tanks usually hold enough compressed air:

For one stop before needing to be refilled.

For several stops before needing to be refilled.

For a day’s worth of braking.

For an unlimited number of stops.

In an air braking system, the air storage tanks can usually hold enough compressed air for the brakes to be used several times.

11. If one air system in a dual air brake system is very low on pressure:

None of the brakes will work at all.

Either the front or rear brakes will not be operating fully.

There will be no noticeable affect.

Lights on the outside of the tractor will flash.

In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.

12. An air brake-equipped vehicle traveling at a speed of 55 mph under ideal driving conditions will need approximately ____ to come to a complete stop.

100 feet

250 feet

300 feet

450 feet

A vehicle's total stopping distance is made up of perception distance, reaction distance, brake lag distance, and braking distance. With all of these factors included, an air brake-equipped vehicle traveling at a speed of 55 mph under ideal driving conditions will need approximately 450 feet to come to a complete stop.

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