Question Emergency brakes are: Answers Not required on trucks. Only required on trailers. Required on tractors. Only required when transporting hazardous materials. Explanation All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. Take a FREE Practice Test Now This questions appears in the following tests: Connecticut Knowledge Test Class A , West Virginia Knowledge Test Class A , Indiana Knowledge Test Class B , Wyoming Knowledge Test Class B , District Of Columbia Air Brakes , New Hampshire Air Brakes , North Dakota Air Brakes , South Carolina Air Brakes ,