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CDL Practice Test: Combination Vehicles

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CDL Practice Test: Combination Vehicles

Combination Vehicles Questions

Click On The Picture To Begin

Good Luck!

What might happen if the trailer is too high when you try to couple?
  • The trailer will be forced downward into the fifth wheel plate, causing damage to the ground or landing gear
  • Modern trucks are installed with a "trailer height icon" which will illuminate on your dashboard
  • It may not couple correctly
  • The fifth wheel plate will automatically adjust to the trailer height
This is a question from page 51 - click here to look up the answer

Quote From Page 75 Of The Illinois CDL Manual:

Check Trailer Height

  • The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. (If the trailer is too low, the tractor may strike and damage the nose of the trailer; if the trailer is too high, it may not couple correctly.)
  • Check that the kingpin and fifth wheel are aligned.

TruckingTruth's Advice:

In addition to incorrect coupling, if a trailer is too high off the ground and you try to back into it, you may cause damage as the rear of your truck cab could strike the front of the trailer. Further, the trailer king pin may become stuck in front of the fifth wheel plate which can be a costly and time wasting error. Before backing under any trailer, it's very important to visually check the trailer height in relation to your tractors fifth wheel.

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Of all truck driver deaths, how many of them are caused as a result of truck rollovers?
  • Rollover accidents rarely result in death
  • More than half
  • More than 1/4
  • More than 3/4
This is a question from page 48 - click here to look up the answer

Quote From Page 70 Of The Illinois CDL Manual:

More than half of truck driver deaths in accidents are the result of truck rollovers

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What are the two main types of a jackknife?
  • Steer jackknife and drive jackknife
  • Drive wheel jackknife and trailer wheel jackknife
  • Tractor jackknife and trailer jackknife
  • Front jackknife and rear jackknife
This is a question from page 48 - click here to look up the answer

Quote From Page 71 Of The Illinois CDL Manual:

Tractor Jackknife: Rear tractor wheels locked up or spinning.

Trailer Jackknife: Trailer wheels locked and sliding

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When does a trailer jackknife most often occur?
  • All trailers, regardless of weight or cargo placement, have an equal chance of jackknifing
  • When the trailer is empty
  • When the trailer is loaded to half of its maximum weight
  • When the trailer is fully loaded to maximum weight
This is a question from page 48 - click here to look up the answer

Quote From Page 71 Of The Illinois CDL Manual:

When the wheels of a trailer lock up, the trailer will tend to swing around. This is more likely to happen when the trailer is empty or lightly loaded. This type of jackknife is often called a "trailer jackknife"

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Which type of combination vehicle experiences the worst type of Rearward Amplification?
  • All trucks, regardless of how many trailers, experience the same amount of Rearward Amplification
  • Trucks pulling 2 trailers
  • Trucks pulling 1 trailer
  • Trucks pulling 3 trailers
This is a question from page 48 - click here to look up the answer

Quote From Page 70 Of The Illinois CDL Manual:

The rear trailer is twice as likely to turn over as the tractor. You can see that triples have a rearward amplification of 3.5. This means you can roll the last trailer of triples 3.5 times as easily as a 5-axle tractor semi.

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What is a way to properly stop a trailer skid?
  • Try to stop the truck as quickly as possible by pressing as hard as you can into the brake pedal
  • Use the trailer hand brake to help straighten out the trailer
  • There is no way to stop a trailer skid once it begins
  • Release the brakes to get traction back
This is a question from page 48 - click here to look up the answer

Quote From Page 71 Of The Illinois CDL Manual:

Following is the procedure for stopping a trailer skid:

1. Recognize the skid. The earliest and best way to recognize that the trailer has started to skid is by seeing it in your mirrors. Any time you apply the brakes hard, check the mirrors to make sure the trailer is staying where it should be. Once the trailer swings out of your lane, it is very difficult to prevent a jackknife.

2. Stop using the brake. Release the brakes to get traction back. Do not use the trailer hand brake (if you have one) to "straighten out the rig." This is the wrong thing to do because the brakes on the trailer wheels caused the skid in the first place. Once the trailer wheels grip the road again, the trailer will start to follow the tractor and straighten out.

TruckingTruth's Advice:

Make certain you glance in your mirrors while stopping in slick conditions. It is very important to catch a jackknife early. The more the trailer swings into a jackknife, the harder it will be to recover.

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How much space should be visible between the upper and lower fifth wheel?
  • There should be space visible, but it should be less than 1 inch
  • There should be 1 to 2 inches of space visible
  • There should be 2 to 4 inches of space visible
  • There should be no space visible
This is a question from page 52 - click here to look up the answer

Quote From Page 77 Of The Illinois CDL Manual:

Inspecting Coupling

  • Use a flashlight if necessary.
  • Make sure there is no space between upper and lower fifth wheel. If there is space, something is wrong (kingpin may be on top of closed fifth wheel jaws; trailer would come loose very easily).
  • Go under trailer and look into the back of the fifth wheel. Make sure the fifth wheel jaws have closed around the shank of the kingpin.
  • Check that locking lever is in the "lock" position.
  • Check that safety latch is in position over locking lever. (On some fifth wheels, the latch must be put in place by hand.)
  • If the coupling is not right, do not drive the coupled unit; get it repaired.

TruckingTruth's Advice:

No space should ever be visible between the fifth wheel plate and the trailer. Be sure you visibly inspect the fifth wheel, as well as the king pin and locking jaws every time you hook to a new trailer. It's also a great idea to get into the habit of pulling against the trailer by leaving the trailer brakes on and slightly tugging on the trailer. This will help insure that you are properly connected. Dropped trailers are very common in the trucking industry, simply because drivers become lazy and don't visually check the truck / trailer connection.

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Which of the following can help reduce the chance of a truck rollover?
  • Look far enough down the road to avoid being surprised and having to make a sudden lane change
  • Slow down to a safe speed before going into a turn
  • All of these can help reduce the chance of a truck rollover
  • At night, drive slow enough to see obstacles with your headlights before it is \ too late to change lanes or stop gently
This is a question from page 48 - click here to look up the answer

Quote From Page 70 Of The Illinois CDL Manual:

Steer gently and smoothly when pulling trailers. If you make a sudden movement with your steering wheel, you could tip over. Follow far enough behind other vehicles (at least 1 second for each 10 feet of your vehicle length, plus another second if going over 40 mph). Look far enough down the road to avoid being surprised and having

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