Air Brake Coach
TrailersQuestion 40 of 116

In cold weather, why do drivers hold the red button while they pull the yellow button?

  1. To charge the tractor tanks
  2. To test the low air alarm
  3. To keep the trailer brakes released so the linings do not freeze to the drums
  4. To apply the trailer brakes
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Correct answer: To keep the trailer brakes released so the linings do not freeze to the drums

This applies the tractor park brakes and keeps the trailer park brakes released.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 6: Tractor and trailer circuits, page 64

Practice trailers

Questions last reviewed: 18 October 2026