You're driving an articulated lorry that has 3 air lines connected to the trailer. What's the purpose of the red line? You're driving an articulated lorry that has 3 air lines connected to the trailer. What's the purpose of the red line?

• Possible answers:

   
• A. It's the emergency line
• B. It's the service line
• C. It's the auxiliary line
• D. It's the electrical line