Doubles And Triples Free CDL Practice Tests
Page 2

Prepare For The Doubles And Triples Portion Of Your CDL Written Exams

Doubles And Triples Questions

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If the dolly has spring brakes, release them with:
  • The emergency air line
  • The dolly parking brake control
  • The air tank petcock
  • The parking brake release knob
Click here to look up the answer

From The CDL Manual

Release dolly brakes by opening the air tank petcock. (Or, if the dolly has spring brakes, use the dolly parking brake control.)

Next
To position the converter dolly over short distances you can:
  • Call a friend
  • Move it by hand
  • Get your dispatcher to help
  • Ask the shipper to do it
Click here to look up the answer

From The CDL Manual

If the distance is not too great, wheel dolly into position by hand so it is in line with the kingpin.

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Next
When connecting converter dolly to the front trailer, support gear should be:
  • Removed
  • Raised
  • Half-way up
  • Lowered
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From The CDL Manual

Hook dolly to front trailer.

  • Lock pintle hook.
  • Secure converter gear support in raised position.
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Next
When coupling, correct trailer height should:
  • Completely clear the dolly
  • Be 4.5 feet off the ground
  • Raise slightly when dolly moves under it
  • Require high RPM's to get under it
Click here to look up the answer

From The CDL Manual

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.)

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Next
After coupling, the air shut-off valves at the back of the first trailer should be:
  • Half-open
  • Closed
  • Disconnected
  • Open
Click here to look up the answer

From The CDL Manual

Open shut-off valves at rear of first trailer (and on dolly if so equipped).

Prev
Next
A visual inspection after coupling should show that:
  • There is space between the upper and lower fifth wheel
  • Landing gear is completely lowered
  • The locking jaws have closed on the kingpin
  • The locking jaws are open
Click here to look up the answer

From The CDL Manual

Raise landing gear slightly off ground to prevent damage if trailer moves.

Make visual check of coupling. (No space between upper and lower fifth wheel. Locking jaws closed on kingpin.)

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Next
You can test whether the trailer air system is charged by:
  • Looking at your air gauges
  • Pumping the brakes repeatedly
  • Trying to pull the trailer
  • Opening the emergency line shut-off
Click here to look up the answer

From The CDL Manual

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.

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Next
When coupling or uncoupling, trailer or dolly wheel should always be:
  • Half-flat to avoid rolling
  • Free-rolling
  • Raised off the ground
  • Locked and/or chocked
Click here to look up the answer

From The CDL Manual

Connect converter dolly to rear trailer:

Make sure trailer brakes are locked and/or wheels chocked.

Prev
Next
When uncoupling twin trailers you should park:
  • At a 45 degree angle to the trailer
  • In a straight line on firm level ground
  • On an uphill incline
  • In a truck stop parking lot
Click here to look up the answer

From The CDL Manual

Uncouple rear trailer:

Park in a straight line on firm level ground.

Prev
Next
When uncoupling the rear trailer, which of these should be done first?
  • Apply rig parking brakes
  • Pull tractor, trailer and dolly out
  • Lower trailer landing gear
  • Disconnect dolly air and electric lines
Click here to look up the answer

From The 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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