Air Brake Coach
InspectionQuestion 76 of 116

You apply the foot or hand valve with both air lines off the trailer. What must you find?

  1. Air leaks from the supply line
  2. The red button pops in
  3. The yellow button pops out
  4. No air leaks from the open trailer service line
Show answer

Correct answer: No air leaks from the open trailer service line

The tractor protection valve must close the service line. No air should leak from it.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Air Brake Practical Test (DPLS0003): Tractor protection system, page 123

Practice inspection

Questions last reviewed: 18 October 2026