Types of Chain Controls:
During the winter months, motorists may encounter traction chain controls in the mountain areas within California. When chain controls are established, signs will be posted along the road indicating the type of requirement. There are three requirements in California.
Requirement One (R1): Chains, traction devices or snow tires are required on the drive axle of all vehicles except four wheel/ all wheel drive vehicles.
Requirement Two (R2): Chains or traction devices are required on all vehicles except four wheel/ all wheel drive vehicles with snow-tread tires on all four wheels.
(NOTE: Four wheel/all wheel drive vehicles must carry traction devices in chain control areas.)
Requirement Three (R3): Chains or traction devices are required on all vehicles, no exceptions.
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 sidewall.