Combination Vehicle Test

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When uncoupling, it's a good practice to...

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If you cross your air lines on a new trailer with spring brakes...

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When traveling under 40 mph, you should follow other vehicles...

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In order to supply air to the trailer, you must first...

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If one of the glad hands on your blue air line is missing a seal...

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When you inspect the coupling, check to ensure that...

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The trailer hand valve should be used...

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Which one of the following statements about tractor protection valves is NOT true?

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You can damage the landing gear if you...

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Which one of the following is controlled by the foot brake?

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When coupling the trailer, back up slowly until...

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The earliest way to notice a trailer skid is...

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A king pin is...

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The trailer should be lowered so that...

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Which of the following steps comes first?

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Before you begin coupling...

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The trailer air supply control...

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In order to inspect the coupling you should...

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You should crank the landing gear until...

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The fifth wheel should be checked to see if...

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You should not back a tractor under a trailer until the whole air system is:

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You are coupling a semi trailer to your tractor but have not yet backed under. The trailer is at the right height when:

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Which part of the kingpin should the locking jaws close around?

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When you get ready to back under the semi trailer you should line up:

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How should you test the tractor semi trailer connection for security?

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When should you use the hand valve to park a combination vehicle?

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You supply air to the trailer tanks by:

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Why should you be sure that the fifth wheel plate is greased as required?

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After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by:

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There are two things that a driver can do to prevent a roll over. They are: (1) Keep the cargo as close to the ground as possible; and (2):

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Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer?

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The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.

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The front trailer supports are up and the trailer is resting on the tractor. Make sure:

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You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:

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When backing under a tractor under a trailer you should expect:

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You are coupling a tractor to a semi trailer and have backed up but are not under it. What should you hook up before backing under?

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You have coupled with a semi trailer. In what position should you put the front trailer supports before driving away?

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Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is ____; the service line is ____.

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Which of these statements is true?

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You are coupling a tractor and semi trailer and have connected the air lines. Before backing under the trailer, you should:

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When uncoupling, if you park the trailer at an angle...

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If you start a trailer skid you should...

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When coupling the glad hands, you should NOT do the following...

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If you cross connect the two air lines the following will result...

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When rolling up the landing gear to complete the coupling process...

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A device which connects the service and emergency air lines from the truck to the trailer is called...

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The service air line is controlled by...

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To prevent rollovers, remember to...

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"Off-tracking" occurs when you go around a corner and...

50 / 60

Large combination vehicles take longer to stop...

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Before you back under a trailer, make sure the:

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If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?

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The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than ____ psi per minute.

54 / 60

In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife. Which of these statements is true?

55 / 60

The driver crosses the air lines when hooking up to an old trailer. What will happen?

56 / 60

The hand valve should be used:

57 / 60

The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than ____ psi per minute.

58 / 60

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that:

59 / 60

You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and:

60 / 60

Semi trailers made before 1975 that are equipped with air brakes:


Free Online Combination Vehicles CDL Practice Test questions and answers to help you pass the Combination Vehicles DMV exam. 

To drive a commercial vehicle AND pull any kind of trailer, you must pass the Combination Vehicles written CDL exam. Combination vehicles are usually heavier, longer, and require more driving skill than single commercial vehicles. This means that drivers of combination vehicles need more knowledge and skill than drivers of single vehicles. You must understand the important safety factors that apply specifically to combination vehicles. Our CDL Combination Vehicles practice tests will prepare you to pass the exam.