State Highway Systems

State Highway Systems:

            In each state a system of roads has been designated by the legislature as a state highway system. Proportions of the total state road mileage under state have assumed vary from 4 to 89% with an average of 19%. Except where the state has assumed primary responsibility for almost all roads, these routes were generally selected as those of primary interest to the state as a whole, as contrasted with roads primarily serving local needs. These state systems usually incorporate the interstate system, the federal-aid primary system, some routes from the federal-aid secondary systems, and other mileage as well. The combined length of the 50 state highway systems is 781,000 mi including about 74,000 mi of extensions into cities some 110,000 mi of the state systems have only gravel, stone, slag, or soil surfaces.