Tennessee Code Title 54. Highways, Bridges and Ferries § 54-10-104

(a) All roads laid off and worked under this chapter shall be known and classified as roads of the first, second, third and fourth class.

(b) Roads of the first class shall be not more than one hundred feet (100′) nor less than twenty-four feet (24′) wide; roads of the second class, not more than forty feet (40′) nor less than eighteen feet (18′) wide; roads of the third class, not more than thirty feet (30′) nor less than fourteen feet (14′) wide; and roads of the fourth class, not more than twenty feet (20′) nor less than ten feet (10′) wide.

(c) All roads of the first class shall have worked a roadbed of at least twenty feet (20′) as the minimum width for first class roads, sixteen feet (16′) for roads of the second class, twelve feet (12′) for roads of the third class, and eight feet (8′) for roads of the fourth class; and, in constructing the roadbed, concrete, broken stones or gravel or other material approved by the department of transportation shall be used, when concrete, broken stones, gravel or other approved material can be conveniently obtained, to form the surface; provided, that where it is possible and practicable, the roadbeds shall be graded with a fall of one inch (1″) to the foot from the center of road to the ditches.

(d) Overseers shall also maintain ditches at each side of the roadbed adequate to drain the roadbed.

(e) The county legislative body may require sections of roads near populous cities to have roadbeds graded to any width not beyond the maximum width allowed in this section for all roads of the class; and when the condition of the road requires it, timbers shall be employed to construct the roadbed in whatever way the commissioner may direct, and, if practicable, the commissioner may have wet or spouty places underdrained by tile draining.