With winter conditions already affecting Colorado’s mountain highways, the Colorado Department of Transportation (CDOT) is reminding commercial motor vehicle (CMV) drivers that the state’s chain season has begun. The department emphasized the importance of preparation for safety on the roads.
This year marks the second season under Colorado’s updated chain law, known as the “Must Carry Law.” Signed by Governor Jared Polis in 2024, this regulation requires all CMV drivers to carry tire chains from September 1 through May 31. The law applies to vehicles weighing more than 16,000 pounds used for commerce or transporting at least 16 passengers, including the driver, on public highways. Drivers who fail to carry chains may face fines of $500, and those who block roadways could be fined up to $1,000 plus a surcharge.
A map is available outlining which roads require CMVs to carry chains or alternative traction devices regardless of current weather conditions. These include sections of I-70 and several state highways such as Highway 9 and US routes 40, 50, 160, 285, and 550. Additional fact sheets are accessible on CDOT’s Freight Mobility website.
Colorado’s mountainous terrain presents challenges due to steep grades and unpredictable weather. Commercial vehicles and buses have a significant impact on these roads when chains are required. Vehicles without proper traction can cause closures that disrupt transportation of goods and people across the state.
CMV drivers typically check weather forecasts before starting their routes to adjust schedules around storm systems and ensure they have chains ready for use. When storms occur, drivers often stop at chain-up stations—sometimes after dark or in freezing temperatures—to install chains before continuing at reduced speeds over steep grades. After passing hazardous sections, they must remove the chains before resuming normal travel. These requirements add to existing rest mandates and long working hours but help keep Colorado’s roads open and maintain connections for mountain communities during severe weather.
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