CDL · Combination vehicles
Many combination vehicles use color-coded air lines so the two are not confused. Which colors are typically used?
Correct answer: Emergency line red, service line blue.
Answer options
- AEmergency line black, service line yellow
- BEmergency line red, service line blue Correct
- CEmergency line blue, service line red
Why
By common convention the red line is the emergency (supply) line and the blue one is the service (control) line. Mixing them up when coupling can keep the trailer brakes from working properly, so check each connection.
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
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