Question Which of the following is not a part of an air brake system? Answers A service brake system A parking brake system An emergency brake system An axle brake system Explanation Air brakes consists of three separate braking systems: the service brake system, the parking brake system, and the emergency brake system. Take a FREE Practice Test Now This questions appears in the following tests: Texas Knowledge Test Class A , Georgia Air Brakes , New York Air Brakes , North Carolina Air Brakes , Wisconsin Air Brakes , Wyoming Air Brakes ,