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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Maryland CDL knowledge test. The MD CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Maryland CDL Manual. Take this MD CDL practice test now to prepare for the actual air brakes test!
1. When you push the brake pedal down, air brakes work:
only when ABS is working.
after about 15 seconds.
after a short delay.
2. After starting the engine, oil pressure should rise to a normal level:
within seconds.
within 2 minutes.
within 3 miles.
within 6 minutes.
3. Axle weight is:
the weight transmitted to the ground by one axle or one set of axles.
the weight of all the axles added together.
the value specified by the manufacturer as the loaded weight of one axle.
the maximum safe weight your tires can carry at a specified pressure.
4. The maximum leakage rates per minute after the initial pressure drop are:
1 psi for single vehicles and 2 psi for a combination of 2 vehicles.
4 psi for single vehicles and 2 psi for a combination of 2 vehicles.
5 psi for single vehicles and 6 psi for a combination of 2 vehicles.
3 psi for single vehicles and 4 psi for a combination of 2 vehicles.
5. When the wheels of a trailer lock up:
ABS will increase stopping power.
the trailer will tend to swing around.
the vehicle will gradually come to a complete stop.
All of the above.
6. Pressing and releasing the brake pedal unnecessarily can:
apply more air pressure.
causes all the air to be lost.
causes friction, which slows the vehicle.
let air out faster than the compressor can replace it.
7. Too little weight on the driving axles can cause:
longer stopping distances.
poor traction.
poor visibility.
mechanical damage.
8. After supplying air to the trailer brake system, you should check the brake system for crossed air lines by:
checking the air brake system pressure gauge for signs of major air loss.
shutting the engine off so you can hear the brakes.
applying and releasing the trailer brakes and listening for the sound of trailer brakes.
All of the above.
9. You are driving on a steep downgrade. If your safe speed is 35 mph, you should apply the brakes when your speed reaches:
45 mph
30 mph
25 mph
35 mph
10. Your vehicle has air brakes. To stop, you should:
pull the parking brake control knob out.
release the accelerator, push in the clutch, and shift to Neutral at the same time.
push the brake pedal down.
pump the brake pedal 3 times.
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MD Air Brakes CDL Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
Number of questions: 25
Correct answers to pass:20
Passing score:80%
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