Practice question

For the Washington CDL Air Brakes knowledge test, when uncoupling a trailer with air brakes, what should you do BEFORE disconnecting the glad hands?

  1. Drain all air tanks
  2. Apply the trailer parking (spring) brakes by pulling the red trailer air supply knob out, then disconnect the glad hands
  3. Start the engine
  4. Apply the foot brake hard

Answer: B — Apply the trailer parking (spring) brakes by pulling the red trailer air supply knob out, then disconnect the glad hands

The correct answer is shown above. Try the full quiz for additional practice.

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