Tennessee Code Title 54. Highways, Bridges and Ferries § 54-18-206

(a) After the public hearing, the legislative body may adopt, by resolution or ordinance, the map as certified by the planning commission as the official map.

(b) Any proposed addition, change or modification of the certified map that is not in accordance with the major highway plan shall be submitted to the planning commission for its approval before any decision by the legislative body on the addition, change or modification.

(c) The planning commission shall have thirty (30) days after the submission within which to send its report to the legislative body.

(d) In the event of the commission's disapproval, the addition, change or modification shall require the favorable vote of a majority of the entire membership of the legislative body.

(e) Amendments of the official map shall be made in the manner required for original adoption.