Tenn. Code Ann. § 65-18-104

Boards, well supported by posts or otherwise, shall be placed, and constantly kept, across each public road, when the same is crossed on the same level by the track of the railway, the boards to be elevated so as not to obstruct travel, and, on each side of such board, there shall be printed in large letters, easily to be seen by the traveler, the words, “Railroad Crossing — Look Out for the Cars.”