Cal. Streets and Highways Code § 30101.8

(a) The commission may grant toll-free and reduced-rate passage on all toll bridges under its jurisdiction to class I vehicles occupied by three or more persons, including the driver, and to buses. For bridges within the area under the jurisdiction of the Metropolitan Transportation Commission, the Bay Area Toll Authority may grant toll-free and reduced-rate passage. (b) Notwithstanding subdivision (a), tolls on the bridges shall be maintained at rates sufficient to meet any obligation to the holders of bonds secured by a pledge of bridge toll revenues, as set forth in any bond resolution, indenture, or covenants, and the commission shall revise or eliminate any toll-free or reduced-rate toll schedule adopted pursuant to subdivision (a) as necessary to ensure compliance with those obligations. (c) If the commission grants toll-free and reduced-rate passage pursuant to subdivision (a), the commission shall also grant the same toll-free and reduced-rate passage to class I vehicles designed by the manufacturer to be occupied by no more than two persons, including the driver, if these vehicles are occupied by two persons, including the driver.