Cal. RTC § 7286.65

(a) Upon the affirmative vote of two-thirds of the directors of the Peninsula Corridor Joint Powers Board, a joint powers authority formed pursuant to the Joint Exercise of Powers Act (Chapter 5 (commencing with Section 6500) of Division 7 of Title 1 of the Government Code), the board may, by resolution and consistent with subdivision (b), submit to the voters of the Counties of San Francisco, San Mateo, and Santa Clara a regional measure proposing only a retail transactions and use tax, at a rate not to exceed 0.125 percent and in accordance with the Transactions and Use Tax Law (Part 1.6 (commencing with Section 7251) of this code) and Article XIII C of the California Constitution, with net revenues from the tax to be used by the board for the operating and capital purposes of the Caltrain rail service.

(b) The measure shall only be submitted to the voters upon approval by the boards of supervisors of the Counties of San Francisco, San Mateo, and Santa Clara, consistent with each county’s applicable procedures, and approval by the San Francisco Municipal Transportation Agency, the San Mateo County Transit District, and the Santa Clara Valley Transportation Authority by a majority vote of each transportation entity’s governing board.

(c) The measure shall be approved if two-thirds of all of the voters voting on the measure approve it.

(d) The board may impose a retail transactions and use tax pursuant to subdivision (a) that, in combination with all taxes imposed in accordance with the Transactions and Use Tax Law (Part 1.6 (commencing with Section 7251)), exceeds the limit established in Section 7251.1.