Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 90, § 1I

Notwithstanding the definition of “Motorcycle” in section 1, the registrar of motor vehicles may register a 3-wheeled motor vehicle as a motorcycle on which the operator and passenger ride within an enclosed cab, if the vehicle's manufacturer has issued a certificate of origin indicating the vehicle meets Federal Motor Vehicle Safety Standards for a motorcycle and if the vehicle is designed by the manufacturer to be operated on public ways. If the registrar determines that the vehicle can attain a speed of at least 30 miles per hour but cannot exceed 40 miles per hour, he may restrict its use on public ways. If the vehicle was previously registered, the registrar may register the vehicle as a motorcycle if the owner provides documentation, satisfactory to the registrar, that the vehicle was previously registered in this or another state as a motorcycle. The registrar may adopt reasonable rules and regulations concerning requirements for registration, equipment, inspections and insurance. Every person authorized and registered to operate such a vehicle upon a way shall not operate the vehicle in excess of 40 miles per hour and shall have the right to use all public ways except limited access or express state highways where signs specifically prohibiting bicycles, mopeds or low-speed vehicles have been posted and shall not operate the vehicle on a portion of a way where the speed limit increases beyond 40 miles per hour. This shall not prohibit a vehicle described in this section from crossing a public way at an intersection where the public way to be crossed has a posted speed limit between 40 and 55 miles per hour, provided the public way the low-speed vehicle is traveling on and the public way the low-speed vehicle is crossing the intersection to, both have a speed limit no higher than 40 miles per hour and the intersection is controlled by traffic signals or stop signs. Such limitations as to the use of public ways may be conspicuously printed on the registration certificate of the vehicle by the registrar. The registrar may issue a distinctive registration plate for such vehicle indicating its speed restrictions.