Drivers heading up Big Cottonwood or Little Cottonwood canyon east of Salt Lake City can be held to winter-tire rules before the first flake lands. The Utah Department of Transportation says it may put restrictions in place up to 24 hours before a storm begins, and on these two roads the tire minimum is 5/32 inch of tread. Both canyons are the strictest category in the state’s system.
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Utah is one of several Western states where a NOAA outlook for Nov. 18-24 flags higher terrain for heavy snow. The Wasatch Mountains, which hold both canyons, sit in the slight-risk category, so the traction rules are worth reading ahead of any ski trip rather than at the canyon mouth, where cars are already queued.
Three alert levels and the 24-hour lead
UDOT’s Cottonwood Canyons traction law page describes a ladder of three alerts. A Weather Alert tells drivers to check conditions. Be Traction Law Ready means qualifying tires or carried devices are required before entering the canyon. Traction Devices Required means devices must be installed on vehicles that need them. Restrictions apply whenever the beacons outside the canyons are flashing, and the canyons are a Class 3 segment, the strictest tier.
A separate UDOT page on snow tire, chain and traction device requirements carries the same timing warning: UDOT or law enforcement decides when conditions call for devices, notice goes out through road signs, message boards, the UDOT traffic app and social media, and drivers may need to comply up to 24 hours before a storm. Neither page describes road closures, which is why the rules here are better understood as entry conditions than as shutdowns.
The 5/32-inch tread rule and what each vehicle type needs
Tires alone qualify only with at least 5/32 inch of tread. Below that depth, the law calls for traction devices: chains, cables, snow socks or studs. Chains, cables and snow socks do not need to be on the wheels until conditions warrant, but they must be in the vehicle.
For vehicles under 12,000 pounds, UDOT sorts requirements by drivetrain. All-wheel-drive and four-wheel-drive vehicles need M+S or three-peak mountain snowflake tires on all wheels with at least 5/32 inch of tread, or traction devices on at least two wheels. Two-wheel-drive vehicles need three-peak mountain snowflake tires on all wheels at that tread depth, or devices on at least the drive wheels. Vehicles rated at 12,000 pounds or more need devices on at least two drive tires, or on all rear drive tires without all-wheel or four-wheel drive, and officials may restrict commercial vehicles even when they comply.
Autoblog’s Nov. 10 report on the snow outlook, written by co-editor-in-chief Adam Lynton, repeats the 24-hour window and the 5/32-inch figure and notes that some rental companies at Salt Lake City’s airport offer pre-inspected vehicles carrying a UDOT sticker on the windshield. UDOT’s own page says vehicles with qualifying tread can obtain a sticker that speeds inspection.
Autoblog’s report makes a point that surprises many drivers: Colorado’s traction rules do not specify a drivetrain, and the Colorado Department of Transportation only recommends all-wheel or four-wheel drive, so an all-wheel-drive SUV on worn or summer tires still fails the requirement. Utah’s canyon rules do vary by drivetrain, but the same logic holds. Drivetrain helps a vehicle accelerate and little else, and the 5/32-inch minimum is a measurement of the rubber, not of the badge on the tailgate. A tread-depth gauge costs a few dollars and settles the question before the drive.
Enforcement at the canyon mouths and the storm outlook
Officers may check vehicles during both the Be Traction Law Ready and Traction Devices Required alerts. Cottonwood Heights police cover the mouth of Big Cottonwood on State Route 190, Sandy City police cover Little Cottonwood on State Route 210, and the Salt Lake County Sheriff’s Office assists at the Snowbird Entry 1 merge and in both canyons. The focus falls on the morning uphill and evening downhill commutes. Drivers who need chains must leave the line and put them on at designated chain-up areas.
UDOT’s page lists no dollar amount for a violation, saying only that the Utah Highway Patrol or a local agency may issue a citation for an infraction. Colorado, by contrast, publishes figures: the Colorado Department of Transportation lists a $100 fine plus a $33 surcharge for standard noncompliance.
Cost is the other practical question for visitors who arrive without gear. Chains, cables and snow socks all satisfy the law when tread falls short of 5/32 inch, and the UDOT page notes that chains can be installed at designated chain-up areas rather than in the travel lanes. Skiers who rent a car in Salt Lake City should ask the rental company about tread and tire ratings before leaving the lot.
On weather, the Climate Prediction Center’s outlook issued Nov. 10 lists higher elevations of the Wasatch Mountains under a slight risk of heavy snow for Nov. 18-24. A week-two product carries wide uncertainty, so no restriction date can be inferred from it, and UDOT has announced none. The open question for skiers is how many of those storm days arrive with enough lead for the 24-hour notice to matter.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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