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. This questions appears in the following tests: District Of Columbia Class A Knowledge Test District Of Columbia Air Brakes Minnesota Air Brakes Nevada Class B Knowledge Test Nevada Air Brakes New Hampshire Class B Knowledge Test New Jersey Air Brakes South Dakota Class A Knowledge Test Tennessee Class B Knowledge Test Tennessee Class B Knowledge Test Utah Air Brakes