Illinois CDL Practice Exam

The emergency air lines in a trailer's air system are typically associated with the color red. This color coding is part of a standardized system designed to make it easier for drivers and maintenance personnel to quickly identify the components of the braking system. The red color signifies a crucial function: the emergency air line is responsible for supplying air to the trailer's brake system if there is a failure in the primary system. This is essential for maintaining safety on the road, as it allows the trailer's brakes to engage if the connection to the tractor is lost or if the primary air system fails. Understanding this color coding can help drivers troubleshoot problems or perform maintenance more effectively.