Tennessee Code Title 65. Public Utilities and Carriers § 65-6-203

(a) The minimum overhead clearance above railroad tracks which are used or purported to be used for transporting freight cars shall be twenty-two feet (22′). Structures constructed prior to April 13, 1949, may be maintained at such clearance as was lawful at the time of construction.

(b) The overhead clearance above the top of the rail of such tracks located inside of buildings may be reduced to seventeen feet (17′); provided, that this clearance shall apply only to tracks operating within the buildings; and provided further, that when an overhead clearance of less than twenty-two feet (22′) exists on tracks inside such buildings, all cars, trains, motors, engines or equipment shall be brought to a stop before entering such buildings.