Chapter 3. Can My Vehicle Be Registered? 3. Three-Wheeled Motorcycles Three Wheeled Vehicles, such as the Polaris Slingshot and the Campagna T-Rex, have been certified by the Manufacturers to NHTSA as motorcycles. These vehicles may have certain automobile design elements, but they can only be registered as motorcycles. Drivers of these vehicle need to follow all motorcycle rules, wear a DOT approved helmet, and have the proper motorcycle license or permit. For a full list of motorcycle rules and requirements, please refer the customer to the online Motorcycle Manual. Examples of Three-Wheeled Motorcycles: Polaris Slingshot right Campagna T-Rex below 05/15https://www.mass.gov/doc/motorcycle-manual/download?_ga=2.109610764.828674685.1644244756-775329760.1614954446