The California Vehicle Code, Section 558 defines a snow-tread tire as follows:
"A 'snow-tread tire' is a tire which has a relatively deep and aggressive tread pattern compared with conventional passenger tread pattern". Snow-tread tires can be identified by examining the sidewall of the tire where the letters MS, M/S, M+S or the words MUD AND SNOW have been stamped into the sidewalls.
TIRE TRACTION DEVICES
The California Vehicle Code, Section 605 defines tire traction devices as follows:
"Tire Traction Devices are devices or mechanisms having a composition and design capable of improving vehicle traction, braking and cornering ability upon snow or ice-covered surfaces. Tire traction devices shall be constructed and assembled to provide sufficient structural integrity and to prevent accidental detachment from vehicles. Tire traction devices shall at the time of manufacture or final assembly, bear a permanent impression indicating the name, initials or trademark of the assembling company or primary manufacturer, and the country in which the devices were manufactured or assembled in final form."
If you would like to view a full version of the California Vehicle Code it can be located at the following location, under California Law: http://www.leginfo.ca.gov
The Department of Transportation does not sell nor recommend specific brands of tire chains. It is best to check your vehicle manufacturers specifications for use of tire chains.
TYPES OF CHAIN CONTROL
During the winter months motorists may encounter traction device controls in the mountain areas of California. When chain controls are established, signs along side the road will be opened indicating the type of requirement. There are three requirements in California.
Requirement One (R1): Chains or snow tread tires required. Snow tires must have a tread depth of 6/32" with a "M & S" imprint on the tire's sidewall.
Requirement Two (R2): Chains required on all vehicles except four-wheel drives or all-wheel drives with snow tread tires on all four wheels. NOTE: four-wheel and all-wheel drive vehicles must carry traction devices in chain control areas)
Requirement Three (R3): Chains are required on all vehicles, no exceptions.