When building a doubles combination on a grade (slope), what additional step must be taken before uncoupling the tractor from the first trailer?

When building a doubles combination on a

Multiple choice — select the best answer

ANo additional steps are needed if the trailer parking brake is applied
BBack the combination against a dock wall to prevent movement
CChock all trailer wheels to prevent rolling before the tractor brakes are released
DEngage the tractor's differential lock to hold the combination in place

✓ Correct answer: C. Chock all trailer wheels to prevent rolling before the tractor brakes are released The CDL manual specifies that wheel chocks must be used on any grade before uncoupling because trailer parking brakes alone may not reliably hold a loaded trailer on a slope.

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When building a doubles combination on a grade (slope), what additional step must be taken before uncoupling the tractor from the first trailer?

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