Question Emergency brakes: Answers Are not required on trucks. Are only required on trailers. Are required on tractors. Are optional. Explanation All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force. This questions appears in the following tests: Arkansas Class B Knowledge Test Arkansas Air Brakes Colorado Air Brakes District Of Columbia Air Brakes District Of Columbia Air Brakes Florida Air Brakes Indiana Class B Knowledge Test Indiana Class B Knowledge Test Kansas Air Brakes Massachusetts Air Brakes Massachusetts Air Brakes Mississippi Bus New Hampshire Air Brakes New York Class A Knowledge Test North Carolina Air Brakes North Dakota Class B Knowledge Test Oregon Class B Knowledge Test Pennsylvania Class A Knowledge Test Texas Double Texas Air Brakes Utah Air Brakes West Virginia Double West Virginia Air Brakes