The Texas Highway Trunk System (Trunk System) is a network of rural divided highways that complements and includes the rural portion of the Interstate Highway System. The minimal design criteria for this network specify that each highway should be at least a four-lane divided facility. The Trunk System serves as a principal connector for all Texas cities with over 20,000 population as well as major ports and points of entry to the state. The total mileage of the Trunk System, as stated in TxDOT Minute Order 910209, is limited to 11,500 miles.