Illinois CDL Practice Exam

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Prepare for the Illinois CDL Exam. Utilize our comprehensive quiz featuring flashcards and multiple choice questions. Enhance your understanding and readiness for the exam with detailed explanations. Ace your CDL test and start your career in commercial driving!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

Which hose coupler color is used specifically for the service lines in a trailer's air lines system?

Yellow
Blue
Green
Black

The correct answer is: Blue

The color blue is specifically used for the service line in a trailer's air line system. This standardization helps drivers and maintenance personnel quickly identify the function of the hoses, ensuring safety and efficiency during the coupling and uncoupling process. The blue color clearly indicates that it is meant for the service brakes, while other colors differentiate between different functions, such as emergency lines. This consistent use of color coding contributes significantly to the safe operation of commercial vehicles.