Question What is a retarder? Answers A device that prevents a vehicle from going too fast A device that prevents a vehicle from being too loud A device that improves a vehicle's gas mileage Explanation Retarders help to slow vehicles, reducing drivers' need to use brakes. This questions appears in the following tests: Alabama Passenger Alaska Class A Knowledge Test Connecticut Class A Knowledge Test Hawaii Double Idaho Class A Knowledge Test Kentucky Class B Knowledge Test North Carolina Tank Vermont Class A Knowledge Test Vermont Class A Knowledge Test Vermont Double