Question 38 of 140

You are about to uncouple a trailer parked on a slight grade. Why should you chock the trailer's wheels first?

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It is only necessary in winter weather
It prevents the landing gear from being damaged during uncoupling
To keep the trailer from rolling once it is no longer held in place by the tractor and its own brakes alone
Chocking is only a formality required by some shippers on their own property, not a real safety measure for the driver

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Correct answer to question 38 (Combination Vehicles): To keep the trailer from rolling once it is no longer held in place by the tractor and its own brakes alone

Why

Once the tractor pulls away, the trailer's own parking brake and landing gear are all that hold it in place, and on a grade that may not be enough, so chocks add a margin against rolling.

Updated: November 2026

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You are about to uncouple a trailer parked on a slight grade. Why should you chock the trailer's wheels first?

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