CDL Practice Tests

Combination Vehicle Test










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Question #1 of 54

Combination Vehicles Test Question Image

Describe what the service line is for.


The service line carries air, which is controlled by the foot brake or the trailer handbrake.

The service line carries air, which is controlled by the foot brake.

The service line carries air, which is controlled by the trailer handbrake.

None of the above.



The Combination Vehicle CDL Test

To get your Class A commercial driver's license, you will need to pass the combination vehicle CDL test. We have assembled a practice test that contains all of the combination vehicle test questions and answers that you can use while you prepare. You will need to be able to answer multiple-choice questions similar to the ones below to pass the combination vehicle portion of the CDL test.

  • When is a trailer jackknife most likely to happen?
  • What is off-tracking?
  • Which air supply line carries air that is controlled by the foot brake?
  • After coupling, how much space should be between the upper and lower fifth wheel?
  • Which air supply line carries air to the trailer air tanks?
  • Where are ABS malfunction lamps located?
  • How do you perform a tractor protection valve test?
  • How do you perform a trailer emergency brake test?
  • Where are shut-off valves located on combination vehicles?
  • What is a bobtail?
  • Name two things that you can do to prevent a rollover?
  • Describe what the trailer air supply control does?
  • Why should you never use the trailer hand valve while driving?
  • How can you test that air flows to all trailers?
  • What is the purpose of the emergency air supply line?
  • Why should you never back under a trailer at an angle?
  • What is the “Crack the whip effect?”
  • Using dummy couplers will help prevent what?
  • How can you attempt to recover from a trailer skid?

If you understand how to perform these tests and can answer all of these combination vehicle questions, and more, we do not doubt that you will be able to pass the written test to get your commercial driver’s license.



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