Iowa Code § 313.8: Improvement of primary road system.

The department shall proceed to the improvement of the primary road system as rapidly as funds become available therefor until the entire mileage of the primary road system is built to established grade, bridged and surfaced with pavement or other surface suited to the traffic on such road. Improvements shall be made and carried out in such manner as to equalize the condition of the primary roads and accessibility for commercial and industrial economic development purposes, as nearly as possible, in all sections of the state.