Which of the following is not part of the four steps to test trailer service brakes?

Answer: D — Continue driving for 5 miles before testing

Testing trailer service brakes focuses on confirming the system is charged and that the service brakes respond correctly when asked to apply. Start by making sure the air pressure is within the normal range so the brakes can release and engage properly. Then release the parking brakes so the service brakes, not the parking brake, do the work. Finally, you pull forward slowly and apply the brakes to check that the braking action is even, smooth, and responsive, with no pulling to one side or unusual noise. Continuing to drive for miles before testing isn’t part of this procedure. Waiting to test after a long drive can hide leaks or brake issues and isn’t how you verify the system’s immediate reliability.