Should the trailer hand brake be applied when a trailer starts to jackknife?
Answer: B
No, the brakes need to be released to help straighten the trailer.
When a wheel is locked up and in a skid, the brakes must be released to allow the wheel to turn and straighten the vehicle. Therefore, any brakes to the trailer need to be released and not applied.
All choices
- AYes, applying the brake will help to straighten the trailer.
- BNo, the brakes need to be released to help straighten the trailer.
- CYes, the brakes will help stop the trailer before it hits the tractor.
Why the other answers are wrong
A. Yes, applying the brake will help to straighten the trailer.
Choice A is wrong because applying the trailer hand brake during a jackknife can worsen the skid and prevent straightening.
C. Yes, the brakes will help stop the trailer before it hits the tractor.
Choice C is wrong because applying brakes during a jackknife does not help stop the trailer before impact but can cause loss of control.
CDL Combination Vehicles Test Info
Questions on Exam
20
Passing Score
80%
Time Limit
Typically 30 minutes; varies by testing location
The Combination Vehicles test content is federally standardized, so this question applies in every state. Age limits, fees, and testing procedures do vary — check your state's CDL requirements.
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More CDL Combination Vehicles Practice Questions
- Why should you lock the tractor glad hands to each other (or dummy couplers) when you are not towing a trailer?
- After connecting the air lines but before backing under the trailer you should:
- The crack-the-whip effect is related to:
- Sudden turns or aggressive braking will have the greatest effect on which trailer?
- Which task is NOT performed during the tractor protection valve test?