There is created hereby a county road administration board consisting of nine members who shall be appointed by the executive committee of the Washington state association of counties. Prior to July 1, 1965 the executive committee of the Washington state association of counties shall appoint the first members of the county road administration board: Three members to serve one year; three members to serve two years; and three members to serve three years from July 1, 1965. Upon expiration of the original terms subsequent appointments shall be made by the same appointing authority for three year terms except in the case of a vacancy, in which event the appointment shall be only for the remainder of the unexpired term in which the vacancy has occurred.