Winter chain controls are a fact of North State work, on the I-5 north of Redding and on SR-299, SR-44 and SR-36. Caltrans posts them in three levels. At R-1, the rules generally call for a truck towing a trailer to chain one drive axle and a braked trailer to chain at least one of its axles, even while lighter vehicles on snow tires go without. At R-2, the exception is typically limited to a four-wheel or all-wheel drive vehicle with snow-tread tires on all four wheels, which is still expected to carry chains. At R-3, Caltrans expects every vehicle to chain.
A crew that tows equipment over the mountains in winter needs chains sized for every drive axle and every braked trailer, and drivers who've practiced putting them on. Writing that into a winter driving rule, along with when crews stay home, is the kind of control fleet safety programs underwriters often credit describes.