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CDL Practice Test: Doubles And Triples

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CDL Practice Test: Doubles And Triples

Doubles And Triples Questions

Click On The Picture To Begin

Good Luck!

Should you pull a dolly out from under a trailer before you disconnect it from the trailer in front?
  • No, the dolly should be removed after all trailers have been dropped to avoid damaging the trailer or dolly
  • Removing the dolly before disconnecting is simply personal preference and it doesn't matter much either way
  • No, you should never leave the rear trailer without a dolly attached to it
  • Yes, that way you can use the truck and first trailer to pull the dolly away from the rear trailer
This is a question from page 57 - click here to look up the answer

Quote From Page 81 Of The Illinois CDL Manual:

Uncouple rear trailer:

  • Park in a straight line on firm level ground.
  • Apply parking brakes so rig will not move.
  • Chock wheels of second trailer if it does not have spring brakes.
  • Lower landing gear of second semitrailer enough to remove some weight from-dolly.
  • Close air shut-offs at rear of first semitrailer (and on dolly if so equipped).
  • Disconnect all dolly air and electric lines and secure them.
  • Release dolly brakes.
  • Release converter dolly fifth wheel latch.
  • Slowly pull tractor, first semi-trailer and dolly forward to pull dolly out from under rear semi-trailer.
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Why do you need to manage your space better while pulling doubles/triples?
  • Doubles / triples take up more space in turns
  • All of these answers are correct
  • Doubles / triples require more stopping distance to avoid a jackknife
  • Doubles / triples tend to be blown around more during windy conditions
This is a question from page 55 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

Doubles and triples take up more space than other commercial vehicles. They are not only longer, but also need more space because they cannot be turned or stopped suddenly. Allow more following distance. Make sure you have large enough gaps before entering or crossing traffic. Be sure you are clear at the sides before changing lanes.

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Next
All of these methods can be used to secure a second trailer before coupling, except:
  • Chock the wheels
  • Make sure the trailer spring brakes are locked
  • If the second trailer does not have spring brakes, drive the tractor close to the trailer, connect the emergency line, charge the trailer air tank, and disconnect the emergency line
  • Back another trailer to the rear of the trailer you want to hook to which will act as a brace and keep the trailer from rolling
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

  • Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.)
  • Make sure trailer brakes are locked and/or wheels chocked.
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Next
The shut-off valves on the middle trailer when pulling triple trailers should be in which position?
  • Both the service line and emergency line should be in the closed position
  • The service line should be open but the emergency line should be closed
  • Both the service line and emergency line should be in the open position
  • The service line should be closed but the emergency line should be open
This is a question from page 59 - click here to look up the answer

Quote From Page 83 Of The Illinois CDL Manual:

Check air flow to all trailers: Use the tractor parking brake and or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red "trailer air supply" knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.

TruckingTruth's Advice:

Unless it is the very last trailer, all shut-off valves should remain in the open position so that all trailers have proper airflow in the air brake system.

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Next
Which of these steps for uncoupling the converter dolly is correct?
  • Disconnect safety chains
  • Release converter gear spring brakes
  • Lock the pintle hook on first semitrailer
  • Quickly pull clear of the dolly
This is a question from page 57 - click here to look up the answer

Quote From Page 81 Of The Illinois CDL Manual:

Uncouple converter dolly:

  • Lower dolly landing gear
  • Disconnect safety chains.
  • Apply converter gear spring brakes or chock wheels.
  • Release pintle hook on first semitrailer.
  • Slowly pull clear of dolly.
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Next
What is a converter gear or dolly?
  • A special accessory used to supply hydraulic pressure to the rear trailer brakes
  • A special device to indicate any airline failures or leaks in the rear most trailer
  • A coupling device of one or two axles and a fifth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a double bottom rig.
  • An anti-jackknife braking system similar to ABS used in the second and/or third trailer
This is a question from page 56 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

A converter gear or dolly is a coupling device of one or two axles and a fifth wheel by which a semitrailer can be coupled to the rear of a tractor-trailer combination forming a double bottom rig.

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When pulling two or more trailers, the shut off valves on the first trailer should be in the following positions:
  • Both the service line and the emergency line should be closed
  • Both the service line and the emergency line should be open
  • The service line should be closed and the emergency line should be open
  • The service line should be open and the emergency line should be closed
This is a question from page 59 - click here to look up the answer

Quote From Page 83 Of The Illinois CDL Manual:

Check air flow to all trailers: Use the tractor parking brake and or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red "trailer air supply" knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.

TruckingTruth's Advice:

Unless it is the very last trailer, all shut-off valves should remain in the open position so that all trailers have proper airflow in the air brake system.

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Next
Should the shut-off valves on the rear of the last trailer be open or closed?
  • The service line should be closed and the emergency line should be open
  • The service line should be open and the emergency line should be closed
  • Both the service line and emergency line should be in the open position
  • Both the service line and emergency line should be in the closed position
This is a question from page 59 - click here to look up the answer

Quote From Page 83 Of The Illinois CDL Manual:

Check air flow to all trailers: Use the tractor parking brake and or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red "trailer air supply" knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.

TruckingTruth's Advice:

All shut-off valves on the rear most trailer should always be in the closed position.

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