The county board, in commissioner type counties having a county highway superintendent and in township type counties having adopted a county road unit system as provided in sections 39-1513 to 39-1518, shall:
(1) Have general supervision over all the duties and responsibilities of the county highway superintendent and shall make necessary policies and regulations to effect an efficient road administration in conformity with the laws of the State of Nebraska;
(2) Appoint and fix the salary of a county highway superintendent in counties having a population of less than one hundred thousand inhabitants according to the most recent official United States census; PROVIDED, that in counties having a population of less than eighteen thousand inhabitants and less than five commissioners the appointment of a county highway superintendent shall be optional with the county board unless a petition is filed with the county clerk as provided by section 39-1502; AND PROVIDED FURTHER, that the county board may appoint and fix the salary of a county highway superintendent jointly with one or more other counties and determine the portion of the salary to be paid by the county for its share of the use of a county highway superintendent serving the cooperating counties;
(3) Have authority to coordinate in an effective manner the highway programs and activities of the county with the related activities of the State of Nebraska and all governmental subdivisions thereof;
(4) Have authority to enter into agreements with the federal government or any department or agency of the federal government, the state or any political or governmental subdivision or public corporation of this state, or with a citizen or group of citizens of this state respecting the planning, designating, financing, establishing, constructing, improving, maintaining, using, altering, relocating or vacation of highways, roads, streets, connecting links or bridges, and in such instances may cooperate with the state or with such subdivisions or public corporations on such terms as may be mutually agreed upon; and
(5) Maintain roads in unincorporated areas if such roads are dedicated to the public and are first improved to minimum standards as established by the county board. In a zoning area of a municipality such standards shall be the higher of those established either by the county or the municipality. Future improvements may be undertaken pursuant to the provisions of Chapter 39, article 16.