California Code, Streets and Highways Code - SHC § 30889.3

(a) The authority may grant toll-free passage or may adopt a reduced-rate schedule of tolls for vehicles occupied by three or more persons, including the driver, and for buses crossing the bridges.  The reduced-rate toll for those vehicles shall be determined by the authority in consultation with the department, and may consist of reduced daily tolls or payment in lieu of daily tolls.  If the authority grants toll- free passage or adopts a reduced-rate toll schedule under this subdivision, it shall grant toll-free passage or adopt the same schedule for class I vehicles designed by the manufacturer to be occupied by not more than two persons, including the driver, if these vehicles are occupied by two persons, including the driver.

(b) Tolls on the bridges shall be maintained at rates sufficient to meet any obligations to the holders of bonds secured by the bridge toll revenues, as set forth in any bond resolution or indenture or obligation contained in bonds issued pursuant to the bond resolution or indenture, and the authority shall revise or eliminate the reduced-rate toll schedule adopted pursuant to subdivision (a) as necessary to ensure compliance with those obligations.

(c) The authority may also vary, as it deems advisable, the toll rates applicable to a vehicle operated on the bridges for the carriage of passengers by any municipal or public corporation, transit district, public utility district, political subdivision, or by a transportation company operating under a certificate of public convenience and necessity.  The authority shall consult with the affected operators prior to adopting any toll rate pursuant to this subdivision.