CDL · Combination vehicles
How do you test whether the tractor and semitrailer are securely coupled?
Correct answer: With the trailer brakes locked, pull the tractor gently forward.
Answer options
- AConnect the electrical cord and confirm the trailer lights come on
- BPull out the trailer air supply knob and watch the air gauges
- CWith the trailer brakes locked, pull the tractor gently forward Correct
Why
A gentle forward tug against locked trailer brakes shows whether the fifth wheel jaws are truly holding the kingpin. If the coupling has not locked, the tractor will start to separate from the trailer.
About this question
Topic: Combination vehicles License: CDL
Part of these practice sets:
Where it applies: Asked in every state.
Practice the whole set
This question is part of Trailer Air Lines and Coupling (28 questions). Take the full set and check your score.
Practice Trailer Air Lines and CouplingMore questions from Trailer Air Lines and Coupling
- When you park a tank trailer, what should hold it in place?
- The fifth wheel jaws have closed on the kingpin, but the locking lever is not in the locked position. What does this tell you?
- You have just charged the trailer's air system. How do you verify that the lines were not crossed and that the trailer brakes respond?
- When you look over a fifth-wheel coupling after hooking up, what should you see?
- When the trailer air supply knob is pushed in, what does it do?
- For a secure coupling, the fifth wheel jaws must grip which section of the kingpin?
- Which statement about air-braked semi-trailers built before 1975 is true?
- How should you position the tractor as you prepare to back under a semitrailer?
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