Tennessee Code Title 55. Motor and Other Vehicles § 55-7-207

(a) As used in this section, unless the context otherwise requires, “publicly owned transit system” means a system of vehicles, designed to carry all persons who desire to use the system, over designated routes within a designated area, which is owned or operated by a county or municipality, incorporated or existing under the laws of Tennessee, or any combination thereof, with any other county or counties, municipality or municipalities, intrastate or interstate, or its or their agencies or instrumentalities, including a transit authority created pursuant to title 7, chapter 56 or other operating or management organization created by any such county, municipality or combination for the purpose of managing a public transportation system.

(c) This section shall apply only to buses owned and/or operated by a publicly owned transit system that itself is an agency of a metropolitan government or county or municipality whose population according to the 1970 census exceeds four hundred thousand (400,000) but is less than eight hundred thousand (800,000).