Driving I-70 to the Mountains in Winter: What to Know Before You Go

For most visitors, the trip to Breckenridge, Frisco, Keystone, Copper Mountain or Vail starts on Interstate 70 heading west from Denver. In summer it is a scenic two-hour drive. In winter the same road climbs over the Continental Divide, and snow, traffic and the rules of the road all deserve a little planning. Here is what to know before you set out.

Colorado's traction law on I-70

Every year from September 1 to May 31, a traction law is in place on I-70 between Morrison and Dotsero, the stretch that covers the mountain corridor to Summit County and the Vail Valley. When the Colorado Department of Transportation (CDOT) puts the law into effect for a storm, passenger vehicles need one of the following:

• Tires with at least 3/16 inch of tread that are rated all-weather or winter tires (look for the mountain-snowflake symbol or M+S on the sidewall)
• Or chains, or an approved alternative traction device such as a tire sock, carried in the car

CDOT also recommends an all-wheel-drive or four-wheel-drive vehicle in the mountains whenever possible. In the worst storms CDOT can call a chain law, the last step before a road closes, when every vehicle needs chains or an approved alternative device. Drivers who don't comply can be fined, and the penalty is much higher if an unprepared car ends up blocking a lane.

Renting a car? Check the tires

Many travelers pick up a rental car at Denver International Airport. When you book, ask for an all-wheel-drive or four-wheel-drive vehicle, and before you drive off, look at the tire sidewalls for the M+S or mountain-snowflake marking. A quick check at the counter is easier than finding out at the first snowy hill.

Know the high points

The highway reaches its highest point at the Eisenhower Tunnel, at more than 11,000 feet, where I-70 passes under the Continental Divide just east of Summit County. Heading on to the Vail Valley, the road crosses Vail Pass at more than 10,600 feet. Both stretches can see heavy snow and strong wind when the valleys below are clear, so the weather in Denver tells you little about the weather at the tunnel.

Timing and road checks

Ski-season weekends are the busiest times on I-70. Traffic tends to build heading west on Friday evenings and Saturday mornings, and heading east on Sunday afternoons. Leaving early, traveling midweek or planning a relaxed lunch stop can turn a long crawl into an easy drive.

Before you go, check COtrip, CDOT's traveler information site and app. It shows road conditions, closures, traffic cameras and whether the traction or chain law is in effect, and you can sign up for text or email alerts. The highway sometimes closes for a short time during storms, for crashes or for avalanche control, so build a little slack into your plans.

A few things worth having in the car on any winter mountain drive:

• A full tank of gas before you leave the Denver area
• Water, snacks and warm layers in case you sit in traffic
• A phone charger and an ice scraper
• Sunglasses, since the sun on fresh snow is bright at altitude

Ways to skip the drive

You don't have to drive to enjoy the mountains. CDOT's Bustang runs its West Line along I-70 from Denver toward Grand Junction. Pegasus, a smaller shuttle van that can use the I-70 Mountain Express Lane, runs between Denver and Avon with stops along the way, and Snowstang runs from Denver to select ski areas during the season. Check current schedules before you travel. Once you arrive in Summit County, the free buses and shuttles make it easy to leave the car parked; see our guide to getting around Summit County without a car.

Your first evening at altitude

The drive takes you from about a mile high in Denver to towns that sit well above 9,000 feet in a couple of hours. Plan an easy first evening: drink plenty of water, go light on alcohol and save the big day on the slopes for the morning. Talk to a doctor about any medical questions before your trip.

If you would like oxygen on hand while you settle in, Peak Oxygen delivers in-home and portable oxygen concentrators to homes, condos and hotels across Summit County and the Vail Valley. It is for recreational use at altitude and no prescription is needed. Deliveries do not require you to be present, so your concentrator can be waiting when you arrive. See the towns we deliver to, compare rental options, or book your delivery.