Air Brake Coach
Spring brakesQuestion 18 of 116

At about what pressure does the park control valve normally pop out?

  1. 60 to 80 PSI
  2. 90 to 100 PSI
  3. 120 to 135 PSI
  4. 20 to 45 PSI
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Correct answer: 20 to 45 PSI

When air drops, the spring pushes the spool and button out. This typically happens at 20 to 45 PSI (138 to 310 kPa).

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 5: Park circuit, page 57

Practice spring brakes

Questions last reviewed: 18 October 2026