What should you check before backing under a trailer after coupling a tractor?

Before backing under a trailer after coupling a tractor, it is essential to check the emergency and service air lines. This is crucial because these lines connect the tractor to the trailer's air brake system. Ensuring that the air lines are correctly connected is important for the safe operation of the vehicle.

If the air lines are not properly attached, it could lead to a loss of braking capability on the trailer, creating a dangerous situation while driving. Checking these lines also helps to prevent air leaks, which can compromise braking performance. It is a fundamental safety step to ensure that everything is in good working order before moving the vehicle.

While inspecting the fifth wheel plate for grease, the trailer's load for stability, and the position of the handbrake are all important aspects of pre-trip inspections and safety checks, the primary focus before backing under a trailer is to confirm that the emergency and service air lines are securely connected, ensuring proper function of the braking system and overall vehicle safety.