California Code, Public Utilities Code - PUC § 131241

(a) The county transportation authority shall consist of the members who are elected officials as specified in the county transportation expenditure plan or in the retail transactions and use tax ordinance, and shall be appointed by each constituent local government within 45 days after the authority is created.

(b) At the first meeting of the county transportation authority, one-half of the members, and the odd-numbered member if the membership of the county transportation authority is odd-numbered, shall be selected by lot to serve terms consisting of the remaining months of the current calendar year, if any, plus two years, and the remaining members shall be selected by lot to serve a term consisting of the remaining months of the current calendar year, if any, plus three years. Thereafter, appointments for all members shall be for two-year terms, beginning on January 1.

(c) If any member or alternate member ceases to be an elected official, that member shall cease to be a member of the county transportation authority, and another member shall be appointed for the remainder of the term by the constituent local government that that member represents.

(d) An alternate may be designated for each regular member. A regular member who, pursuant to the county transportation expenditure plan, serves by virtue of holding a specified public office, may designate a person to serve as his or her alternate. In the case of any other regular member, the appointing constituent local government may designate an alternate to the regular appointed member. The alternate's term of office shall be the same as that of the regular member. When the regular member is not present at the meeting of the authority, the alternate may act as the regular member and shall have all the rights, privileges, and responsibilities of the regular member.