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Class 1 Commercial Driver Practice · Question

When uncoupling a semi-trailer, after parking on level ground and applying trailer brakes, what is the next safety step before disconnecting air and electrical lines?

After positioning and applying trailer brakes, the most crucial next step is to lower the landing gear until it firmly contacts the ground, supporting the trail

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Question: When uncoupling a semi-trailer, after parking on level ground and applying trailer brakes, what is the next safety step before disconnecting air and electrical lines?

Answer options:

  • Drive the tractor forward slowly.
  • Retract the landing gear fully. ✅ Lower the landing gear firmly to the ground.
  • Remove the kingpin lock.

Correct answer: Lower the landing gear firmly to the ground.

Explanation: After positioning and applying trailer brakes, the most crucial next step is to lower the landing gear until it firmly contacts the ground, supporting the trailer's weight. This prevents the trailer from falling when the tractor is removed.

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