The state highways and transportation commission shall appoint a secretary who shall serve at its pleasure. The secretary shall keep complete and accurate records of all the proceedings of the commission, shall be the custodian of all books, maps, documents and papers filed with the commission and all orders made by the commission. Under the direction of the commission, the secretary shall have such authority and perform such duties as the commission may require. The secretary may designate one of the clerks in his office to perform the duties of the secretary during his absence, and during such time the clerk so designated shall, while at the office of the commission, possess the powers of the secretary.