Question What is a drawback of retarders? Answers They may not be permitted everywhere. They can help to slow a vehicle. They cannot be turned off. Explanation A retarder is a device that helps to slow a vehicle, reducing the need for a driver to use the brakes. However, these devices can be noisy and are not permitted everywhere. Take a FREE Practice Test Now This questions appears in the following tests: Maryland Knowledge Test Class B , Iowa Double , New Mexico Double , South Dakota Tank , Wyoming Passenger ,