Question Which type of brakes do most heavy-duty vehicles have? Answers Air brakes Solid brakes Liquid brakes Gravity brakes Explanation For safety, most heavy-duty vehicles are equipped with dual air brake systems. This questions appears in the following tests: Colorado Class B Knowledge Test Colorado Air Brakes Delaware Class A Knowledge Test Delaware Air Brakes New Jersey Tank North Dakota Bus Texas Class A Knowledge Test Texas Class B Knowledge Test Texas Air Brakes West Virginia Class A Knowledge Test Wisconsin Double