Practice question

The red 8-sided 'Trailer Air Supply' knob on the dash is:

  1. Pulled out to supply air to the trailer
  2. Pushed in to supply air to the trailer; pulled out to apply trailer emergency brakes
  3. Always left in the out position when driving
  4. A pressure gauge, not a control

Answer: B — Pushed in to supply air to the trailer; pulled out to apply trailer emergency brakes

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

Practice more: Ohio CDL Combination Practice Questions - Ohio CDL Combination Vehicles Test Exam →