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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!

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
  • The service line should be closed and the emergency line should be open
  • Both the service line 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.

Next
Which of these steps about uncoupling the rear trailer is incorrect?
  • Park in a "half circle" on firm level ground
  • Release dolly brakes
  • Release converter dolly fifth wheel latch.
  • Close air shut-offs at rear of first semitrailer (and on dolly if so equipped)
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.
Prev
Next
Do converter dollies have spring brakes?
  • Some converter dollies have spring brakes, but dollies are not required to have them
  • All converter dollies are required to have spring brakes if built after 1975
  • Converter dollies don't ever have spring brakes
  • While some states don't require dollies to have spring brakes, it is required for dollies to have spring brakes on the interstate system
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.

  • Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.
Prev
Next
Why do you need to manage your space better while pulling doubles/triples?
  • All of these answers are correct
  • Doubles / triples take up more space in turns
  • 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.

Prev
Next
How do you check to make sure the trailer height is correct before coupling?
  • The trailer should be slightly higher than the center of the fifth wheel, so the trailer doesn't have to raise up when the dolly is pushed under
  • The trailer landing gear should be lowered completely so that you can push the dolly under the trailer and be ready to drive once attached
  • The trailer must be slightly lower than the center of the fifth wheel, so the trailer is raised slightly when dolly is pushed under.
  • The trailer should be a minimum of 1ft higher than the fifth wheel, so the trailer king pin will not strike the fifth wheel plate and cause damage
This is a question from page 56 - click here to look up the answer

Quote From Page 81 Of The Illinois CDL Manual:

Connect converter dolly to rear trailer:

  • Make sure trailer brakes are locked and/or wheels chocked.
  • Make sure trailer height is correct. (It must be slightly lower than the center of the fifth wheel, so trailer is raised slightly when dolly is pushed under.)
  • Back converter dolly under rear trailer.
  • Raise landing gear slightly off ground to prevent damage if trailer moves.
  • Test coupling by pulling against pin of number two semi-trailer.
  • Make visual check of coupling. (No space between upper and lower fifth wheel. Locking jaws closed on kingpin.)
  • Connect safety chains, air hoses and light cords.
  • Close converter dolly air tank petcock and shut-off valves at rear of second trailer (service and emergency shut-offs).
  • Open shut-off valves at rear of first trailer (and on dolly if so equipped).
  • Raise landing gear completely.
  • Charge trailers (push "air supply" knob in) and check for air at rear of second trailer by opening the emergency line shut-off. If air pressure is not there, something is wrong and the brakes will not work.
Prev
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
  • Both the service line and emergency line should be in the closed position
  • Both the service line and emergency line should be in the open position
  • 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:

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

Prev
Next
Which of the following is true about pulling double or triple trailers?
  • Doubles/triples don't jackknife as easily as single trailer vehicles
  • Doubles/triples are less prone to rollovers than single trailer vehicles
  • Doubles/triples are less stable than other commercial vehicles
  • Doubles/triples are easier to handle in windy conditions than single trailer vehicles
This is a question from page 55 - click here to look up the answer

Quote From Page 80 Of The Illinois CDL Manual:

Take special care when pulling two and three trailers. There are more things that can go wrong, and doubles/triples are less stable than other commercial vehicles. Some areas of concern are discussed below.

TruckingTruth's Advice:

Pulling doubles or triples are much more dangerous in nearly every aspect of driving, which is why they require an additional endorsement. Be extra cautious when driving a truck with two or more trailers.

Prev
Next
Which of these steps for uncoupling the converter dolly is correct?
  • Disconnect safety chains
  • Quickly pull clear of the dolly
  • Release converter gear spring brakes
  • Lock the pintle hook on first semitrailer
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.
Prev
Finish
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