CDL · Doubles and triples
When you drop the rear trailer from a double combination, what should you do with the air shut-off valve at the back of the front trailer?
Correct answer: Close it completely.
Answer options
- AOpen it all the way.
- BClose it completely. Correct
- COpen it just slightly.
Why
Before the dolly's air lines are disconnected, the shut-offs at the back of the front trailer must be closed. If they were left open, air would rush out of the disconnected hoses and bleed down the brake system.
About this question
Topic: Doubles and triples License: CDL
Part of these practice sets:
Where it applies: Asked in every state.
Practice the whole set
This question is part of Coupling Doubles and Converter Dollies (28 questions). Take the full set and check your score.
Practice Coupling Doubles and Converter DolliesMore questions from Coupling Doubles and Converter Dollies
- When you uncouple twin trailers, which of these is the final step?
- In the official CDL manual, the section on doubles and triples generally explains coupling and uncoupling for which combinations?
- You are getting ready to hook a second trailer to your rig. What can you use to hold that trailer in place?
- Compared with an A-dolly, what is the main thing a B-dolly or C-dolly adds?
- Which of these steps do you carry out first when uncoupling standard doubles?
- What should you use to hold the second trailer still before you couple it to the rest of the doubles combination?
- Which statement about a converter dolly is true?
- What is the reason for moving a dolly clear of the rear trailer before releasing it from the lead trailer?
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