California Code, Public Utilities Code - PUC § 99501

(a) “Taxing entity” means a county other than a county with a transit development board or a county under the jurisdiction of a county transportation commission created pursuant to Division 12 (commencing with Section 130000), a city and county, a county transportation commission, a transit development board, a transit district, or a city with a population in excess of 500,000 located within a transit district. The population of a city shall be as determined by the last preceding federal census or by a subsequent census validated by the Demographic Research Unit of the Department of Finance.

(b) “Transit vehicle” means a vehicle, including, but not limited to, one operated on rails or tracks, which is used for public transportation service and which carries more than 10 persons, including the driver.