Air Brake Coach
System failuresQuestion 42 of 116

A failure occurs in the primary circuit. What keeps the spring park brakes released?

  1. The caging bolts
  2. Air pressure from the secondary circuit
  3. The trailer supply valve
  4. The hand valve
Show answer

Correct answer: Air pressure from the secondary circuit

Park circuit air comes from the higher tank. The secondary circuit keeps the park brakes released.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 7: System failures, page 69

Practice system failures

Questions last reviewed: 18 October 2026