49 CFR 372.113: Providers of recreational activities.

Transportation by a motor vehicle designed or used to transport not fewer than 9, and not more than 15, passengers (including the driver), whether operated alone or with a trailer attached for the transport of recreational equipment, is exempted from regulation promulgated pursuant to Part B of Title 49 U.S.C. subtitle IV if:

(a) the motor vehicle is operated by a person that provides recreational activities;

(b) the transportation is provided within a 150 air-mile radius of the location at which passengers initially boarded the motor vehicle at the outset of the trip; and

(c) in the case of a motor vehicle transporting passengers over a route between a place in a State and a place in another State, the person operating the motor vehicle is lawfully providing transportation of passengers over the entire route in accordance with applicable State law.