Question

You are coupling a tractor to semitrailer and have backed up but are not under it. What should you hook up before backing under?

A) The emergency and service brakes lines
B) The electrical service cable
C) Nothing, Back up and lock the fifth wheel

Answer 1

Before backing under a semitrailer, you should connect the emergency and service air brake lines to ensure safety and check for any leaks, and then lock the fifth wheel. Additionally, don't forget to connect the electrical service cable.

Step-by-step explanation:

When you are coupling a tractor to a semitrailer, and you have backed up but are not yet under it, you should connect the emergency and service air brake lines before backing under the semi-trailer.

This is an essential step to ensure that the trailer brakes are activated in case of an emergency, and also to check for air leaks in the brake system.

Once the air lines are connected and checked, then you can back up to lock the fifth wheel. It's also important to connect the electrical service cable to power the trailer's lights and other electrical systems before starting your trip.