Tenn. Code Ann. § 55-15-103

“Motor vehicle,” as used in this chapter, includes all vehicles propelled by any power other than muscular power, except traction engines, road rollers, fire and police vehicles, ambulances, agricultural tractors, tractor cranes, steam shovels, road building machinery, electric trucks with small wheels used in factories, warehouses, and railroad stations and operated principally on private property, and such vehicles run only upon rails or tracks.