Quick answer

Colorado's Passenger Vehicle Traction Law is in effect every Sept. 1 through May 31 on I-70 between Dotsero and Morrison, and CDOT can activate it on any state highway during a storm. To comply, a 4WD or AWD vehicle needs tires with at least 3/16-inch tread that are rated M+S, all-weather or winter (mountain-snowflake). Any other vehicle needs chains or an approved traction device such as an AutoSock. Since Aug. 6, 2025, 2WD vehicles can no longer comply with tires alone. Breaking the law costs about $133, or about $657 if your vehicle blocks the road.

Updated Sept. 29, 2026, from CDOT, Colorado State Patrol and state law.

Every fall, thousands of Denver drivers head up I-70 without realizing the Traction Law is already in effect. It changed in 2025, and the change matters most for owners of front-wheel-drive cars. Here's what the law requires this winter, how it differs from the Chain Law, what it costs to ignore it and how to check your tires in two minutes.

Key takeaways

The Traction Law is always in effect on I-70 from Dotsero to Morrison from Sept. 1 through May 31.

AWD or 4WD with at least 3/16-inch tread on M+S, all-weather or winter tires complies.

Since August 2025, 2WD vehicles need chains or an approved traction device, even with snow tires.

Fines start around $133 and jump to about $657 if you block the road.

When and where the Traction Law applies

The law is in effect on I-70 between Dotsero (milepost 133) and Morrison (milepost 259) every day from Sept. 1 through May 31, whether or not it's snowing. CDOT can also activate it on other state highways when weather requires. Check COtrip.org, the free COtrip Planner app or call 511 before you go.

Where the Traction Law is in effect all season

I-70 from Dotsero (exit 133) to Morrison (exit 259), Sept. 1 through May 31. Landmarks shown by approximate milepost.

DotseroMile 133

VailMile 176

Vail PassMile 190

FriscoMile 201

Eisenhower TunnelMile 214

GeorgetownMile 228

Idaho SpringsMile 240

MorrisonMile 259

What complies after the 2025 change

Senate Bill 25-069 took effect Aug. 6, 2025. Before it, a 2WD car with good snow tires could meet the Traction Law. Now, as Colorado State Patrol puts it, there is no tire-only option for 2WD vehicles. The law also requires rental car companies to tell renters about the chain law between Sept. 1 and May 31, and it created CDOT permits for roadside chain-installation services.

Your vehicle	Tires or equipment	Complies?
4WD or AWD	At least 3/16-inch tread, rated M+S, all-weather, or winter with the mountain-snowflake symbol	Yes
4WD or AWD	Tread below 3/16 inch, or summer tires	No
2WD (front- or rear-wheel drive)	Any tires, including winter tires	No, since Aug. 2025
Any vehicle	Chains or an approved traction device, such as an AutoSock, on two or more drive tires	Yes

Before Aug. 6, 2025

2WD with M+S or winter tires and 3/16-inch tread could comply.

Since Aug. 6, 2025

2WD needs chains or an approved traction device, whatever tires it has.

Traction Law vs. Chain Law

CDOT retired the old "Code 15," "Code 16" and numbered commercial codes in 2020 and replaced them with plain-language names. Here's what each one means.

Passenger Vehicle Traction Law

Formerly Code 15. AWD or 4WD with qualifying tires, or chains or a traction device on any other vehicle. In effect all season on I-70 and whenever CDOT activates it elsewhere.

Passenger Vehicle Chain Law

Formerly Code 16. Every passenger vehicle, including AWD and 4WD, needs chains or an approved traction device. CDOT calls it the final safety measure before closing the highway.

Commercial Vehicle Chain Law

Formerly Codes 17 and 18. Applies to vehicles over 16,000 lb or carrying 16 or more passengers, which need chains on at least four drive tires. Colorado has 130 chain stations, 22 on the I-70 mountain corridor.

What it costs, in fines and in time

What it costs if you don't comply

Fine plus surcharge, approximate

Passenger vehiclesCommercial vehicles

Passenger vehicle, not equipped~$133

$100 fine + $33 surcharge

Passenger vehicle that closes a lane~$657

$500 fine + $157 surcharge

Commercial vehicle, not equipped~$579

$500 + $79

Commercial vehicle blocking the road~$1,157

$1,000 + $157

Sources: CDOT; Colorado State Patrol.

The bigger cost is everyone's time. CDOT reported that in one December, Traction Law violations caused 26% of the crashes on the I-70 mountain corridor and nearly 288 hours of lane closures. On a single day, 19 of the 22 vehicles CDOT helped after spinouts had bald tires.

In other words, one car on worn tires can close a lane for hundreds of drivers, which is exactly what the higher lane-closure fine is meant to discourage.

Tires are what actually stop you

AWD and 4WD help you get moving, but they don't help you stop or turn. That's the tires' job, which is why the law sets a tread minimum and why CDOT pushes winter tires so hard.

Stopping distance on snow from 60 mph

Feet to stop

Summer tires800+ ft

All-season tires669 ft

Winter tires310 ft

Source: CDOT.

Stopping distance on wet pavement from 50 mph

Feet to stop

Worn tires130 ft

New tires85 ft

Source: CDOT.

How to check your tread

Try the quarter test

CDOT's quick check: put a quarter upside down in the tread, Washington's head first. If the top of his head is visible anywhere, you need new tires. Check several spots on every tire.

Then measure 3/16 inch

The quarter test shows roughly 1/8 inch of tread, less than the 3/16-inch legal minimum. An inexpensive tread gauge, or any tire shop or service department, can measure it precisely.

Read the sidewall

Look for M+S, the mountain-snowflake symbol or an all-weather rating.

If you drive 2WD, carry a device

Keep chains or an approved traction device in the car and practice putting them on in your driveway, not on the shoulder of I-70.

Our factory-authorized service departments at Emich Volkswagen, Emich VW of Boulder, Emich Kia and Emich Chevrolet can check your tread and tires before your first ski trip. Find service near you.

Buying a car for Colorado winters?

The simplest way to comply for the whole season is AWD or 4WD with good tires. That describes 83% of the used vehicles across our four Denver-area stores, from AWD SUVs and EVs to 4WD pickups.

Colorado-ready used vehicles

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Frequently asked questions

When is Colorado's Traction Law in effect?

Every year from Sept. 1 through May 31 on I-70 between Dotsero and Morrison. CDOT can also activate it on any other state highway when weather conditions require.

Does AWD meet Colorado's Traction Law?

Yes, if the tires have at least 3/16-inch tread and are rated M+S, all-weather or winter with the mountain-snowflake symbol.

Can a front-wheel-drive car with snow tires drive I-70 in winter?

Only with chains or an approved traction device. Since Aug. 6, 2025, under SB25-069, 2WD vehicles can no longer meet the Traction Law with tires alone.

What is the fine for violating the Traction Law?

About $133 ($100 plus a $33 surcharge) for a passenger vehicle, and about $657 ($500 plus a $157 surcharge) if your vehicle causes a lane closure.

What is the difference between the Traction Law and the Chain Law?

Under the Traction Law, AWD and 4WD vehicles with qualifying tires comply. Under the Passenger Vehicle Chain Law, every passenger vehicle needs chains or an approved traction device. The Chain Law is CDOT's last step before closing the highway.