California Code, Public Utilities Code - PUC § 29750

If district bonds for the acquisition or construction of rapid transit facilities have not been voted by the electors within five years of the creation of the district, the board of directors may call an election for the purpose of submitting to the voters of the district the question of whether the district will be dissolved.  Upon the filing with the secretary of the district of a petition signed by voters within the district equal in number to at least 25 percent of the total vote cast in the district for all candidates for Governor at the last preceding general election at which a Governor was elected, asking that the question of dissolution of the district be submitted to the voters of the district, the board shall call an election for that purpose.