Each commissioner’s term of office is four years; provided, however, that the commissioners appointed by the Mayor of the City of Oakland and the Mayor of the City of San Jose shall have an initial term of office ending in February 2015. A commissioner appointed as a public officer vacates his or her commission seat upon ceasing to hold such public office unless the appointing authority consents to completion of the term of office. Commissioners shall be selected for their special familiarity with the problems and issues in the field of transportation.