Tenn. Code Ann. § 47-26-812

Gross weights for truck or tractor trailer vehicles shall be determined by axle limitations as prescribed in § 55-7-203(b)(6), and adding an additional five hundred pounds (500 lbs.) thereto when the natural resources product is transported over a street or highway other than the portion designated as the interstate system. A three percent (3%) tolerance, over the maximum gross weight as prescribed in § 55-7-203(b)(6), may be permitted when the natural resources product is transported over a street or public highway other than the portion designated as the interstate system. A certified public weigher will not be subject to any liability for measurement variance which falls within such three percent (3%) tolerance, but shall be responsible for measurement variance in excess of the three percent (3%) tolerance.