Winter driving
Do you need snow tires for I-70 and US-285? Colorado's Traction Law explained
Colorado's Traction Law sets the tire rules for every winter drive from Denver into the mountains, and CDOT updated it in November 2025.
A live person answers. Not a robot, not a phone tree. Updated September 2026.
Photos: Aerial of golden fall aspens and a mountain road, Taylor Brandon (Unsplash).
Under the updated Colorado Traction Law, every tire needs at least 3/16-inch tread and a winter, all-weather or M+S rating, or the vehicle needs chains or an approved traction device on two or more drive tires. The law runs every September 1 through May 31 on I-70 between Dotsero and Morrison, and CDOT activates it on any state highway, including US-285, during storms.
3/16-inch minimum.
Every tire needs at least 3/16-inch of tread under the updated Traction Law.
Winter, all-weather or M+S.
The mountain-snowflake icon, an all-weather rating or an M+S mark all comply.
Drivetrain does not count.
CDOT applies the law to all 4WD and AWD vehicles. Tires decide compliance.
September 1 to May 31.
Every year between Dotsero and Morrison.
What does the Colorado Traction Law require?
- 3/16-inch tread. That is the minimum under the updated Traction Law CDOT announced on November 20, 2025.
- The right tire type. Winter tires with the mountain-snowflake icon, all-weather rated tires or mud-and-snow (M+S) tires.
- Or chains. Chains or an approved alternative traction device on two or more drive tires also comply.
- 4WD and AWD are covered too. CDOT states the law applies to all 4WD and AWD vehicles, regardless of drivetrain.
Check tread with a gauge before September. 3/16-inch is the line.
When and where is the Traction Law in effect?
- I-70, September 1 through May 31. The law runs every year on the I-70 Mountain Corridor between Dotsero and Morrison.
- Any state highway during a storm. CDOT activates the Traction Law and Chain Law on any state highway, including US-285 over Kenosha Pass (9,984 feet).
- The Chain Law comes next. CDOT calls the Passenger Vehicle Chain Law the final safety measure before a highway closes.
- The fine rises if you block the road. A vehicle without proper equipment that closes a travel lane draws a larger fine. CDOT's Traction Law page lists the current amounts.
Check COtrip.org or call 511 before you leave Denver.
What makes I-70 west of Denver hard in winter?
- The Eisenhower-Johnson Tunnel sits high. Its average elevation is 11,112 feet, per CDOT.
- Snow piles up at the tunnel. CDOT puts snowfall there at 315 inches, or 26 feet, from November through April.
- Metering at the tunnel. CDOT meters eastbound traffic. Drivers stop an average of 20 minutes, and CDOT puts the actual added delay at 3.5 minutes.
- Floyd Hill construction. CDOT's Floyd Hill project between Evergreen and Idaho Springs passed its halfway mark in July 2026. Westbound opens in its new alignment by the end of 2027, and the whole project finishes in 2029.
How does the Traction Law work on US-285 to Conifer and Bailey?
- No seasonal Traction Law. The September-to-May rule is written for I-70. On US-285, CDOT activates the law during storms.
- Kenosha Pass is the high point. US-285 crosses Kenosha Pass at 9,984 feet, past Bailey toward Fairplay.
- Check before you leave. COtrip.org and the 511 line post Traction Law and Chain Law activations for US-285 and I-70.
Buying on US-285 or I-70? Ask the Kenna Real Estate Group at 303-955-4220 how the driveway and road handle snow.
Questions
Quick answers.
Do I need snow tires in Colorado?
Not by law. When the Traction Law is active you need 3/16-inch tread and a winter, all-weather or M+S rating, or chains.
What is the tread depth for the Colorado Traction Law?
At least 3/16-inch on every tire.
Does AWD meet the Colorado Traction Law?
Not by itself. CDOT applies the law to 4WD and AWD vehicles, and tread and tire type decide compliance.
When is the Traction Law in effect on I-70?
Every September 1 through May 31 between Dotsero and Morrison.
Does the Traction Law apply on US-285?
Yes, when CDOT activates it. CDOT activates the Traction Law and Chain Law on any state highway.
Sources
- CDOT, new Traction Law (2025-11-20)
- CDOT, Traction and Chain Law
- CDOT, Eisenhower-Johnson Tunnel
- CDOT, I-70 metering
- CDOT, Floyd Hill project
- Kenosha Pass
Rules, rates and dates change. The county, town or state office named above has the current version.
Go deeper
Where to go next.
The map
Where the mountain towns are.
Every pin opens that town's page. Drive times from downtown Denver, without traffic.
- Front Range foothills
- I-70 corridor
- Peak to Peak
- Summit County
- Resort
- Tap a town to open its page
Outline: U.S. Census Bureau. Roads from downtown Denver: OSRM on OpenStreetMap. Town points: OpenStreetMap and USGS. Drive times without traffic.
Private consultation
Ask us about your mountain home.
303-955-4220A live person answers. Not a robot, not a phone tree.
- Every mountain town. Evergreen and Conifer to Summit County and Steamboat.
- Wildfire, water, winter. Insurance, well, septic and access checked before you offer.
- One point of contact. From the first call to the closing table.
Colorado Mountain Home Finder is part of the Kenna Real Estate Group at Keller Williams DTC (KWDTC).