The county executive shall appoint a traffic safety advisory board of fifteen members interested in traffic safety and traffic problems. Each member shall be a resident of Erie county and shall be a qualified elector thereof. At least one of such members shall be a resident of each of the cities contained in the county and at least six of such members shall be residents of the area of the county outside such cities. The said board shall annually elect a chairman, vice chairman and secretary from its members. Meetings of the traffic safety advisory board shall be held at the call of the commissioner of public works or the chairman of such board on three days' written notice mailed to the last known address of such board members. Such board shall have and exercise the powers and duties conferred or imposed upon it by the county charter or this code. The term of office of such members shall be five years. The terms of office of the incumbent members of the traffic safety advisory board shall continue for the periods for which such members shall have been appointed. Vacancies in the membership of the board occurring otherwise than by expiration of term shall be filled by appointment for the unexpired term.