Tennessee Code Title 54. Highways, Bridges and Ferries § 54-5-108

(b) The department has full power, and it is made its duty, acting through its commissioner, to formulate and adopt a manual for the design and location of signs, signals, markings, and for posting of traffic regulations on or along all streets and highways in Tennessee, and no signs, signals, markings or postings of traffic regulations shall be located on any street or highway in the state regardless of type or class of the governmental agency having jurisdiction of the streets and highways, except in conformity with the provisions contained in the manual.