California Code, Vehicle Code - VEH § 35720

(a) Any vehicle which is subject to the provisions of Article 2 (commencing with Section 1031) of Chapter 5 of Part 1 of Division 1 of the Public Utilities Code or any farm labor vehicle.

(b) Any street, road or highway which is not under the exclusive jurisdiction of the board of supervisors enacting such ordinance, except as otherwise provided in Section 35719, or, in the case of any state highway, until such proposed ordinance has been submitted by the board of supervisors to and approved in writing by the Department of Transportation.  In submitting such a proposed ordinance to the department for approval, the board of supervisors shall designate therein, an alternate route or routes for the use of such vehicles which shall remain unrestricted by any local regulation as to weight limits or types of vehicles so long as the ordinance proposed shall remain in effect.  The approval of such proposed ordinances by the Department of Transportation shall constitute an approval by the department of such alternate route or routes so designated.

(c) Any commercial vehicle coming from an unrestricted street, road or highway having ingress and egress by direct route to and from such restricted streets, roads, and highways when necessary for the purpose of making pickups or deliveries of goods, wares and merchandise from or to any building or structure located on such restricted streets, roads or highways or for the purpose of delivering materials to be used in the actual and bona fide repair, alteration, remodeling or construction of any building or structure upon such restricted street, road or highway for which a building permit, if required, has previously been obtained therefor, or vehicles, machinery, or construction equipment used in connection with, the construction, repair or maintenance of such restricted street or public work projects located thereon.

(d) Any vehicle operated as an incident to any industrial, commercial, or agricultural enterprise conducted upon any such street, road, or highway.

(e) Any vehicle owned, operated, controlled, or used by a public utility or licensed contractor in connection with the construction, installation, operation, maintenance, or repair of any public utility facilities or public works projects.

(f) The operation of ambulances or hearses.