Practice question

For an Wisconsin CDL air-brake vehicle, can the trailer hand valve (trolley valve) be used to hold a parked combination vehicle in place?

  1. Yes, always
  2. No — it can release if air leaks; use the parking brake instead
  3. Only on hills
  4. Only when the trailer is empty

Answer: B — No — it can release if air leaks; use the parking brake instead

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