CDL · Combination vehicles
You are coupling to an older trailer and accidentally cross the air lines. What is the result?
Correct answer: If the trailer lacks spring brakes, you could drive away with no trailer brakes.
Answer options
- APressing the brake pedal will apply the trailer's spring brakes rather than its air brakes
- BIf the trailer lacks spring brakes, you could drive away with no trailer brakes Correct
- CUsing the hand valve will set the tractor's brakes rather than the trailer's brakes
Why
Crossed lines send supply air into the service line, so the trailer tanks never fill. A trailer with spring brakes would stay braked and alert you, but an older trailer without them can roll freely, letting you pull away with no trailer brakes.
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
- On a tractor-trailer, what are glad hands used for?
- Which statement about air-braked semi-trailers built before 1975 is true?
- Before the tractor backs under a semitrailer during coupling, how high should the front of the trailer be?
- When the trailer air supply knob is pushed in, what does it do?
- Before coupling, how high should the trailer sit compared with the converter dolly's fifth wheel?
- 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 drive a tractor with no trailer attached, why should its glad hands be locked together or onto dummy couplers?
- When you park a tank trailer, what should hold it in place?
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