Colorado's Traction Law and Chain Law: What Drivers Need to Know This Winter (2026 Update)

I grew up biking, snowboarding, and riding motorcycles in the mountains, so I've driven I-70 in every kind of weather. And every fall, I see the same questions on Reddit from people moving to Colorado. Do I need AWD? Do I need snow tires? Do I have to carry chains?

The answers changed this year, and most of what you'll find online is out of date. Here's what the law actually requires for the 2026-27 season, what it costs if you ignore it, and why it matters far more after a crash than it does at a traffic stop.

What Changed for 2026: Your Tires Matter, Not Your Drivetrain

For years, many Coloradans assumed a Subaru or a four-wheel-drive truck was automatically legal in the mountains. That's no longer true.

In 2025, the legislature rewrote the traction law to focus on tire quality, but the new wording accidentally made it unclear how two-wheel-drive cars could comply. The sponsors admitted the mistake and promised a fix. The fix is House Bill 26-1237, signed on May 5, 2026. It removed the references to four-wheel and all-wheel drive entirely. The rule now applies the same way to every passenger vehicle, whatever its drivetrain.

The Traction Law (Code 15)

When the traction law is active, every passenger vehicle needs one of two things:

1. Qualifying tires with at least 3/16 inch of tread. That means winter tires (the mountain-snowflake symbol), mud-and-snow tires (marked M+S or M/S), or tires the manufacturer rates as all-weather.
2. Chains or an approved alternative traction device, like an AutoSock, on at least two tires.

The traction law is automatically in effect every year from September 1 through May 31 on the I-70 mountain corridor between Dotsero and Morrison. CDOT can also activate it on any state highway when conditions call for it, including US 40 over Berthoud Pass to Winter Park, US 285 toward Fairplay, and even I-25 during a Front Range storm. Check COtrip.org and the overhead message signs before you go.

The Chain Law (Code 16)

The passenger vehicle chain law is CDOT's last step before closing a highway. When it's active, every vehicle needs chains or an approved traction device. Winter tires, AWD, and 4WD don't matter. CDOT says activation is exceedingly rare. The last time was the March 2019 bomb cyclone.

What It Costs If You Ignore It

The base penalty for a traction law violation is a $50 fine plus a $17 surcharge. It gets much steeper if your car gets stuck and blocks a travel lane: up to a $500 fine plus a $157 surcharge. Enforcement is real, too. State Patrol wrote 586 chain and traction law citations last season, 522 of them on I-70, and that was during one of the lowest-snow winters in years.

If You're Moving to Colorado

My short answer to the Reddit question:

• You don't need AWD. You need the right tires. A front-wheel-drive car on good winter tires often handles snow better than an AWD SUV on worn all-seasons.
• Check what you already have. Many all-season tires carry an M+S marking and comply if the tread is deep enough. Look at the sidewall, then measure.
• If you'll be in the mountains often, get winter tires. They're the best option for I-70 in a real storm.
• Carry a traction device anyway. It's your backup if a storm catches you on worn tires, and it's required during the rare chain law.
• Practice putting chains on in your driveway, not on the shoulder of Vail Pass in a blizzard.

For the rest of the new-resident checklist, including which tires to buy, how black ice forms, your DMV deadlines, and the insurance to choose when you register, see my guide on moving to Colorado and driving your first winter.

Why This Matters After a Crash

A $67 ticket isn't the real risk. The real risk is what a traction law violation means when someone gets hurt.

It's evidence of fault. When a driver violates a safety law designed to protect other people on the road, and that violation causes a crash, Colorado law can treat it as negligence per se. A driver who slides into you on bald tires during an active traction law has handed you strong evidence.

"The road was icy" is not a defense. Colorado law requires every driver to drive at a speed that's reasonable for the conditions (C.R.S. § 42-4-1101). The Colorado Supreme Court made this point directly in Bedor v. Johnson (2013). A driver hit an ice patch near Telluride on a road where he knew ice formed, spun across the center line, and hit another car. The jury had been told he wasn't responsible for how he reacted to a "sudden emergency." The Supreme Court reversed and abolished the sudden emergency instruction in Colorado negligence cases altogether. Ice doesn't excuse a driver who wasn't driving for the conditions.

It can cut both ways. If you were the one on bald tires, expect the other driver's insurer to raise it. It only matters if it actually contributed to the crash. Being stopped in traffic on worn tires when someone rear-ends you isn't the same as sliding through an intersection. But under Colorado's comparative fault rule, any share of fault reduces what you recover, and 50% or more bars recovery entirely.

Mountain crashes get complicated fast. Pileups on I-70 can involve a dozen vehicles, out-of-state drivers, rental cars, and commercial trucks, each with a different insurer pointing at everyone else. For what makes truck crashes on the corridor different, see my post on I-70 truck crashes. If a CDOT plow or another government vehicle was involved, you may have only 182 days to give written notice. And if the at-fault driver has minimal coverage, your own UM/UIM coverage matters, which is one more reason to know what "full coverage" actually includes.

If you've been hurt in a winter crash, learn more about how I handle car accident cases.

What It Costs to Hire Me

My fee is 29% pre-litigation and 33% if we sue, compared to the 33-35% and 40-45% most Colorado firms charge. On a $100,000 recovery in litigation, the difference between 33% and 40% is $7,000 that stays with you. See the full breakdown on my fees page.

Colorado Traction Law FAQ

Is AWD or 4WD enough to comply with the traction law?

Not by itself. Under the 2026 update, what matters is your tires: winter, mud-and-snow, or manufacturer-rated all-weather tires with at least 3/16 inch of tread. Without qualifying tires, you need chains or an approved traction device, whatever your drivetrain.

Do all-season tires count?

Often, yes. Many all-season tires carry the M+S (mud and snow) marking and comply if they have at least 3/16 inch of tread. Check the sidewall for M+S, M/S, or the mountain-snowflake symbol, and measure your tread.

When and where does the traction law apply?

It's in effect every year from September 1 through May 31 on I-70 between Dotsero and Morrison. CDOT can also activate it on any state highway when conditions require. Check COtrip.org or watch the overhead signs.

Does the traction law apply to rental cars and out-of-state drivers?

Yes. It applies to the vehicle on the road, not where it's registered or who owns it. Many rental cars come with all-season tires, so check the tread and the sidewall before heading into the mountains.

If a driver with bald tires slid into me, is the crash automatically their fault?

Not automatically, but it's strong evidence. A traction law violation can support a negligence per se claim, and Colorado law requires every driver to drive for the conditions. An icy road doesn't excuse a driver who wasn't equipped or wasn't driving carefully enough for it.