Section 54. The administrator may from time to time, subject to the approval of the secretary, establish within the division such administrative units as may be necessary for the efficient and economical administration of the division and, when necessary for such purpose, may abolish any such administrative unit or may merge any 2 or more units, as the administrator deems advisable; provided, however, that the administrator shall establish the following units: highway engineering, highway construction and highway maintenance. Each such unit shall be under the direction, control and supervision of the director. The director shall assign to all officials, agents and employees of the units their respective duties. The administrator shall prepare and keep current a statement of the organization of the division, of the assignment of its functions to its various administrative units, offices and employees, and of the places at which and the methods whereby the public may receive information or make requests. Such statement shall be known as the division’s description of organization. A current copy of the description of organization shall be kept on file in the office of the state secretary and in the office of the secretary of administration and finance.