Practice question

Pull out the trailer air supply control, or set it in the "emergency" position, when testing:

  1. The trailer emergency brakes.
  2. The parking brake.
  3. The trailer service brakes.
  4. The landing gear.

Answer: A — The trailer emergency brakes.

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

Practice more: Massachusetts CDL Double Test 2 →