Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 90, § 32J

(a) As used in this section, “car-sharing organization” shall mean a membership-based entity with a distributed fleet of private passenger motor vehicles that are made available to its members primarily for hourly or other short-term use through a self-service fully automated reservation system that periodically charges a use-based fee relating to a specific vehicle;  provided, however, that “car-sharing organization” shall not include an arrangement where a separate written agreement is entered into each time a vehicle is transferred to a customer.

(b) Vehicles in a fleet of a car-sharing organization may display private passenger motor vehicle registration number plates issued by the registrar;  provided, however, that a registered vehicle of any such organization which identifies the name of the organization by business markings thereon shall not be required to display a commercial registration plate if the markings are limited to the name, address, telephone number, logo or website address of the organization.