County roads in Smith County, unless posted otherwise, are rated at a gross weight limit of 30,000 lbs. Gross weight is the total weight of the truck or combination, and its load. The Smith County Road and Bridge Department issues free permits for Commercial vehicles to operate on county roadways in excess of the 30,000 lb. limit, as long as the vehicle is in compliance with other previsions of commercial vehicle law. Permits are valid for 90 days and can be renewed. By state law, the county cannot issue a permit for longer than 90 days.