Air Brake Coach
TrailersQuestion 35 of 116

A trailer supply valve does not work properly. What will an enforcement officer do?

  1. Give a warning only
  2. Let you drive to your base
  3. Put the vehicle out of service
  4. Check the hand valve only
Show answer

Correct answer: Put the vehicle out of service

The trailer supply valve is part of the tractor protection system. A fault puts the vehicle out of service.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 6: Tractor and trailer circuits, page 63

Practice trailers

Questions last reviewed: 18 October 2026