It may feel like summer along the Front Range with warm, sunny days stretching into September but in Colorado’s high country, snow is always a possibility. That’s why each year from Sept. 1 through May 31 Colorado’s Chain Law and Passenger Vehicle Traction Law are in effect for all drivers.
“Whether a tractor-trailer or a four-door sedan, snow and ice conditions impact your drive,” said Col. Matthew C. Packard, chief of the Colorado State Patrol (CSP). “If carrying chains or checking your tire tread seems like a hassle, imagine the inconvenience of sitting in traffic due to a crash or being rerouted miles out of your way due to highway closures.”
Colorado’s laws are designed to keep drivers safe and traffic moving when winter weather strikes. Here’s what you need to know:
Requirements for Larger Vehicles (Commercial & Recreational)
As of Aug. 7, 2024, all commercial motor vehicle (CMV) drivers must carry chains while the chain law is in effect. This applies to vehicles over 16,000 pounds or those designed to transport 16+ passengers, including the driver.
Chains or approved alternative traction devices (ATDs) are required on these highways, regardless of weather:
- I-70 west of Morrison (mile point 259) to the Utah border
- CO 9 between Frisco (mile point 63) and Fairplay (mile point 97)
- US 40 from Empire (mile point 256) to the Utah border
- US 50 from Salida (mile point 225) to the Utah border
- US 160 from Walsenburg (mile point 304) to the New Mexico border
- US 285 from Morrison (mile point 250) to the New Mexico border
- All of US 550
Penalties include a $500 fine and a $79 surcharge, or a $1,000 fine and a $157 surcharge if the truck is stuck and blocking traffic.
Requirements for Passenger Vehicles and Light Trucks
All vehicles under 16,000 pounds traveling on I-70 between Morrison (mile point 259) and Dotsero (mile point 133) must be equipped with one of the following from September through May:
- Tire chains for two or more drive tires, or
- An approved ATD, or
- Tires with at least 3⁄16-inch tread depth and rated as All Weather or Mud and Snow (M+S, M/S), or with the snowflake-mountain (“3PMSF”) icon.
Penalty for non-compliance includes a $50 fine and $17 surcharge.
First Chain Check & Recent Enforcement Stats
To kick off the season, the Colorado State Patrol (CSP) held its first Commercial Motor Vehicle Chain Check on Thursday, Sept. 4, 2025, along I-70 near Dotsero. During that chain check 400 drivers were contacted, and 153 total charges were issued. A total of 49 chain violations were recorded and other violations included 51 “port runners” (drivers who were required to stop at the Port of Entry but did not), two seat belt violations, and two commercial motor vehicles taken off the road for operating without a valid CDL. Overall CSP estimates the compliance rate for the operation was about 88 percent.
These stats show that while many drivers are following the rules, violations are still common — and penalties are real when laws are enforced.
How to Stay Informed
Chain law alerts and restrictions are announced by CDOT through:
- Static and electronic roadway message boards
- The 511 traveler information system
- COtrip.org (CDOT’s official travel website)
- Local and statewide media outlets
Snow in September may not be the norm along the Front Range, but it’s far from unusual in Colorado’s mountains. Don’t wait for the first storm to prepare — make sure your vehicle meets traction requirements now so you can travel safely, avoid fines and minimize delays.