Practice question

For the Washington CDL Air Brakes knowledge test, what is an air-over-hydraulic brake system?

  1. A purely hydraulic system
  2. A hybrid system in which air pressure assists the hydraulic master cylinder, used on some smaller CMVs
  3. A system without air at all
  4. A trailer-only system

Answer: B — A hybrid system in which air pressure assists the hydraulic master cylinder, used on some smaller CMVs

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