CDL Vehicle Combination Practice Test

What color is the emergency line on a combination vehicle?

1. Red

2. Blue

3. Green

4. Yellow

The correct answer is: Red

The emergency line on a combination vehicle is red. This color coding is significant because it helps drivers quickly identify and differentiate between the various lines associated with the vehicle’s braking and emergency systems. The red line specifically denotes the emergency air line, which is critical for ensuring that the trailer brakes engage if the connection is lost or the air pressure drops below a safe level. Recognizing the emergency line by its red color is essential for maintaining safety on the road, as it allows drivers to swiftly assess their vehicle's readiness and respond appropriately to any braking emergencies.