Why should you lock the tractor glad hands to each other (or dummy couplers) when you are not towing a trailer?
Answer: A
It will keep dirt or water out of the lines.
Locking the tractor glad hands with each other when not pulling a trailer is the best way to avoid contamination from getting to the coupler and air supply system.
All choices
- AIt will keep dirt or water out of the lines.
- BIf you did not, you could never build system pressure.
- CThe connected brake circuit becomes a backup air tank.
Why the other answers are wrong
B. If you did not, you could never build system pressure.
System pressure can be built without locking the glad hands to each other; locking is to prevent contamination.
C. The connected brake circuit becomes a backup air tank.
The connected brake circuit does not act as a backup air tank; locking glad hands prevents dirt and water entry.
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
- 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?
- What is the purpose of the trailer air supply control?
- What is the most common cause of a tractor-trailer jackknife?