Illinois CDL Practice Exam

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Study for the Illinois CDL Exam. Utilize comprehensive quizzes featuring multiple choice questions with hints and explanations. Gear up for success on your test!

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What is the recommended color for the hose couplers used to connect the service air lines in a trailer's air system?

Red
White
Black
Blue

The correct answer is: Blue

The recommended color for the hose couplers used to connect the service air lines in a trailer's air system is blue. This color designation helps to identify the purpose of the connection quickly and effectively, which is crucial for safety and operational efficiency in the trucking industry. The blue color specifically indicates that the line is used for service brakes, promoting standardization across vehicles and trailers to minimize the risk of confusion during connections and disconnections. In contrast, other colors serve different functions: for instance, red is typically used for emergency brake lines, while black can sometimes represent electrical connections, and white is not commonly associated with air line connections. Standardizing the colors helps ensure that drivers can quickly and accurately connect the correct lines, enhancing safety on the road.