Chains, tires and 4WD: what Utah actually requires
Utah does not require chains all winter. It has a traction law, Utah Administrative Code R920-6, that
UDOT or law enforcement switches on for designated stretches of highway when conditions call for it.
You are told by road signs, message boards, the UDOT Traffic app and UDOT's own social accounts — not by
a website you checked yesterday.
When it is posted, this is the minimum kit, straight from UDOT's traction law summary:
The bit that is specific to this road
UDOT's traction law map classifies segments. Highway 14 from Cedar City east across the plateau
is a Class I segment, where a posted requirement applies to vehicles over 12,000 pounds gross
weight — motorhomes, buses, box trucks, heavy tow rigs. Highway 143 up Parowan Canyon to Brian
Head is Class II, where it applies to every vehicle on the road. If your trip includes a ski day
at Brian Head, that is the drive with the stricter rule, and it is worth knowing before you are sitting at
the bottom of the canyon behind a trooper.
One more piece of internet folklore to clear up: the 5/32-inch tread requirement you will find in Utah
traction-law articles belongs to the Class 3 designation written for Big and Little Cottonwood Canyons
outside Salt Lake City. It does not apply here. What does apply statewide is the plain tread law — any
tire under 2/32 inch is illegal, in any season, and is also the reason a car slides on a grade it should
have climbed.
What all-wheel drive does and does not buy you
All-wheel drive helps you start moving and keeps you tracking on a packed climb. It does nothing for
stopping and nothing for cornering — those are entirely the tires, which is why the traction law is
written about rubber and not about drivetrains. A front-wheel-drive car on true winter tires will
out-drive an all-wheel-drive SUV on worn all-seasons on this road, and the SUV's extra confidence is
exactly what gets it going too fast for the descent into the village.
If you carry chains, fit them at the bottom, in a pullout, before you need them — not on a grade in the
dark with traffic going by. And fit them to the drive wheels: front on a front-wheel-drive car, rear on a
rear-wheel-drive truck.