California Code, Vehicle Code - VEH § 27454

(a) Tire traction devices of reasonable size used to prevent skidding when upon wet surfaces or when upon snow or ice.

(b) Pneumatic tires that have embedded therein wire not to exceed 0.075 of an inch in diameter and that are constructed so that under no conditions will the percentage of metal in contact with the roadway exceed 5 percent of the total tire area in contact with the roadway, except that during the first 1,000 miles of use or operation of the tire, the metal in contact with the roadway may exceed 5 percent of the tire area in contact with the roadway, but shall in no event exceed 20 percent of the area.

(c) Vehicles operated upon unimproved roadways when necessary in the construction or repair of highways.

(d) Traction engines or tractors when operated under the conditions of a permit first obtained from the Department of Transportation.

(f) Pneumatic tires used on an authorized emergency vehicle, as defined in Section 165, containing metal-type studs of tungsten carbide or other suitable material, if the studs are inserted or constructed so that under no conditions will the number of studs or the percentage of metal in contact with the roadway exceed 3 percent of the total tire area in contact with the roadway. Notwithstanding subdivision (e), authorized emergency vehicles are permitted the unrestricted use of studded pneumatic tires throughout the year.