Cal. Pub. Util. Code § 226

(a) “Passenger stage corporation” includes every corporation or person engaged as a common carrier, for compensation, in the ownership, control, operation, or management of any passenger stage over any public highway in this state between fixed termini or over a regular route except those, 98 percent or more of whose operations as measured by total route mileage operated, which are exclusively within the limits of a single city or city and county, or whose operations consist solely in the transportation of bona fide pupils attending an institution of learning between their homes and that institution.
For purposes of this section, the percentage of the route mileage within the limits of any city shall be determined by the Public Utilities Commission on the first day of January of each year, and the percentage so determined shall be presumed to continue for the year.
(b) “Passenger stage corporation” does not include that part of the operations of any corporation or person engaged in the ownership, control, operation, or management of any passenger stage over any public highway in this state, whether between fixed termini or over a regular route or otherwise, engaged in the transportation of any pupils or students to and from a public or private school, college, or university, or to and from activities of a public or private school, college, or university, where the rate, charge, or fare for that transportation is not computed, collected, or demanded on an individual fare basis.
(c) “Passenger stage corporation” does not include the transportation of persons between home and work locations or of persons having a common work-related trip purpose in a vehicle having a seating capacity of 15 passengers or less, including the driver, which is used for the purpose of ridesharing, as defined in Section 522 of the Vehicle Code, when the ridesharing is incidental to another purpose of the driver. This exemption also applies to a vehicle having a seating capacity of more than 15 passengers if the driver files with the commission evidence of liability insurance protection in the same amount and in the same manner as required for a passenger stage corporation, and the vehicle undergoes and passes an annual safety inspection by the Department of the California Highway Patrol. The insurance filing shall be accompanied by a one-time filing fee of seventy-five dollars ($75). This exemption does not apply if the primary purpose for the transportation of those persons is to make a profit. “Profit,” as used in this subdivision, does not include the recovery of the actual costs incurred in owning and operating a vanpool vehicle, as defined in Section 668 of the Vehicle Code.
(d) “Passenger stage corporation” does not include that part of the operations of any corporation or person engaged in the ownership, control, operation, or management of any medical transportation vehicles, including vehicles employed to transport developmentally disabled persons for regional centers established pursuant to Chapter 5 (commencing with Section 4620) of Division 4.5 of the Welfare and Institutions Code.
(e) “Passenger stage corporation” does not include the transportation of persons which is ancillary to commercial river rafting and is for the sole purpose of returning passengers to the point of origin of their rafting trip.
(f) “Passenger stage corporation” does not include social service transportation delivered by a nonprofit social service transportation provider or a locally licensed or franchised for-profit transportation provider which operates, in dedicated vehicles, social service transportation pursuant to contract with a nonprofit social service transportation provider organization as long as the provider does not use a vehicle designed for carrying more than 16 persons, including the driver, or does not operate vehicles which offer transportation services over regularly scheduled or fixed routes.
(g) “Passenger stage corporation” does not include intrastate passenger transportation service conducted pursuant to federal operating authority to the extent that regulation of these intrastate operations by the commission is preempted by the federal Bus Regulatory Reform Act of 1982 (P.L. 97-261), as amended.