Winter Driving to Ski Resorts: Chains, Tires and Rules

By Justin McKelvey · Updated November 7, 2026

State rules at a glance

Rules change, so check the official page for your route before each trip.

Colorado: the I-70 traction law

Per CDOT, the traction law is in effect on I-70 between Morrison and Dotsero generally from September 1 to May 31, and CDOT can put it into effect on any state highway when conditions call for it. When it's active, your vehicle must have one of:

• Winter tires, or all-weather tires marked M+S, M/S or with the mountain-snowflake symbol, with at least 3/16 inch of tread
• Chains or an approved alternative traction device carried in the vehicle, such as certain tire socks on CDOT's approved list

The chain law is the step before a closure in severe storms: every vehicle needs chains or an approved alternative device. CDOT lists fines for not complying, and higher fines if your vehicle blocks a travel lane. Active traction and chain laws are posted on highway signs and on COtrip.org.

AWD or 4WD alone does not satisfy the rule on CDOT's current page; it is the tires that count, though CDOT strongly recommends AWD or 4WD in the mountains.

A common tread check is the quarter test. Put a quarter upside down in the tread; if you can see the top of Washington's head, your tread is likely under 3/16 inch.

Heading to Colorado ski resorts? Flying into Eagle (EGE) or Hayden (HDN) skips most of I-70. See drive or fly to a ski resort.

California: R1, R2 and R3 chain controls

Caltrans sets chain controls on mountain highways such as I-80 and US-50 to Lake Tahoe and US-395 toward Mammoth. Signs show the level in effect. Per Caltrans:

• R1: chains required except on passenger vehicles and light trucks under 6,000 lbs with snow tires on at least two drive wheels. Those vehicles must still carry chains.
• R2: chains or traction devices required on all vehicles except 4WD or AWD vehicles with snow-tread tires on all four wheels. Those 4WD and AWD vehicles must carry traction devices in chain control areas.
• R3: chains or traction devices required on all vehicles, no exceptions.

When chains are required you must stop and put them on, and the speed limit drops to 25 or 30 mph. Caltrans advises always carrying chains that fit your tires and are installed on the drive wheels, so practice putting them on at home, not on a dark shoulder in a storm. See California ski resorts.

Utah: Big and Little Cottonwood Canyons

The roads to Snowbird, Alta, Solitude and Brighton climb steep canyons with avalanche control and frequent storm closures. Per UDOT, when the canyon traction requirements are in effect:

• All tires need at least 5/32 inch of tread.
• 2WD vehicles: 3PMSF (three-peak mountain snowflake) tires on all wheels at minimum, or chains or snow socks on at least two drive wheels.
• AWD and 4WD vehicles: M+S tires on all wheels at minimum. Chains, socks or 3PMSF tires on all wheels give the most reliable traction.

UDOT says requirements can go into effect ahead of a storm, and enforcement happens when the traction lights at the canyon entrance are on. For live updates, UDOT points travelers to @UDOTCottonwoods on social media and its road status page. See Utah ski resorts.

AWD vs 4WD vs snow tires

• Tires matter most. AWD and 4WD help you accelerate and climb, but they do not help you stop or steer on ice. Winter tires do all three better.
• AWD powers all wheels automatically and is common on crossovers and SUVs. Great for snowy roads, but only with good tires.
• 4WD is usually switched on by the driver and is common on trucks and larger SUVs, with more clearance for deep snow.
• Winter tires with the 3PMSF symbol grip far better in cold, snow and ice than all-season tires, and they qualify under Colorado, California and Utah rules. A 2WD car with winter tires often handles better than an AWD car on worn all-seasons.
• Read your sidewall. M+S is common on all-season tires. The mountain-snowflake symbol means the tire passed a snow traction test.

Carrying skis on the roof? See ski racks and roof boxes.

What to keep in the car

• Chains or approved tire socks that fit your tires, plus gloves and a kneeling pad for installing them
• Ice scraper and snow brush
• Small shovel
• Full tank of gas (or a full charge) before you climb. Fill up in the last big town.
• Warm blankets or sleeping bags, extra hats and gloves for everyone
• Water and snacks, especially with kids
• Phone charger and a power bank
• Flashlight or headlamp
• Winter windshield washer fluid
• Jumper cables and a basic first aid kit

Shop tire chains or snow socks for tires if you need them.

Check road conditions before you go

• Colorado: COtrip.org and CDOT's free COtrip Planner app, with road conditions, closures, cameras and a plow tracker.
• California: Caltrans QuickMap, a live map with chain controls, closures, CHP incidents and cameras.
• Utah: UDOT Traffic and its free UDOT Traffic app, plus UDOT Cottonwood Canyons for canyon status.
• Check the snow forecast too. A big storm means powder and slow roads. Every Snow Way resort page shows a 7-day forecast.

Driving a rental car to the mountains

• Reserve AWD or 4WD, but check the tires when you pick it up. Look for the M+S or mountain-snowflake marking and decent tread, and ask for a different car if they don't meet the rules for your route.
• Read the chain rules in your rental agreement. Many rental companies restrict or prohibit chains. Enterprise, for example, says it doesn't provide chains and they can't be put on its cars unless state law requires them. Policies vary by company and location, so ask before you go.
• If the car can't meet the rules, have a backup: a shuttle, a bus, or waiting out the storm.

Driving tips for snowy mountain roads

• Slow down and leave much more following distance than usual.
• Brake and accelerate gently; don't use cruise control on snow or ice.
• Use a lower gear on long downhills instead of riding the brakes.
• Watch for black ice on bridges, shaded curves and in the early morning.
• Give plows plenty of room and never pass them on the right.
• Avoid peak times: weekend mornings heading up and Sunday afternoons heading down are the slowest.

Planning the whole trip? Use the free Ski Trip Planner and see how to plan a family ski trip.