CDL · Doubles and triples
In a double or triple combination, how should you set the shut-off valves located at the back of the rearmost trailer?
Correct answer: Closed, with the valves at the back of every trailer ahead of it left open.
Answer options
- AEither position, provided the tractor protection valve works properly
- BClosed, with the valves at the back of every trailer ahead of it left open Correct
- COpen, so air can escape freely from the rear of the rig at all times
Why
Closing the rear valves on the last trailer keeps air from venting out the back, while the valves on the trailers ahead must be open so air can pass through to the end of the combination.
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 Inspecting Doubles and Triples (15 questions). Take the full set and check your score.
Practice Inspecting Doubles and TriplesMore questions from Inspecting Doubles and Triples
- Which lamp is required on a converter dolly that has an antilock braking system (ABS)?
- Which of these is a key check when you inspect a double or triple rig?
- What tells you that a converter dolly is fitted with antilock brakes (ABS)?
- You are inspecting a converter dolly. What must be true of its pintle hook connection?
- How can you check that air is actually getting all the way to the second trailer?
- On a walk-around inspection, what should be true of every landing gear?
- Federal rules require antilock brakes (ABS) on converter dollies manufactured from which month and year onward?
- How do you confirm that air is reaching every trailer in a double or triple combination?
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