With winter conditions already affecting mountain highways, the Colorado Department of Transportation (CDOT) is reminding commercial motor vehicle (CMV) drivers that the state’s chain season has begun. This comes as Colorado enforces its updated “Must Carry Law” for a second year.
The law, signed by Governor Jared Polis in 2024, requires all CMV drivers to carry tire chains from September 1 to May 31. It applies to vehicles with a combined weight over 16,000 pounds or those transporting at least 16 passengers, including the driver, on public highways. Drivers who do not comply may face fines of $500 for not carrying chains and up to $1,000 plus surcharges if they block the roadway.
A CDOT fact sheet provides further details about the law and lists chain-up stations throughout Colorado. According to CDOT, certain routes—including stretches of I-70 and Highways 9, US 40, US 50, US 160, US 285, and US 550—require CMVs to carry chains or alternative traction devices regardless of current weather conditions.
Colorado’s mountain highways present unique challenges due to steep grades and unpredictable weather. Commercial vehicles without proper traction can cause road closures that disrupt transportation across the state. Chaining up is just one part of preparing for safe winter driving.
Before starting their routes during winter months, CMV drivers check weather forecasts and make sure chains are ready for use. When storms occur, drivers must often stop at chain-up stations—sometimes after dark or in freezing temperatures—to install chains before continuing over steep grades at reduced speeds. After crossing hazardous areas, they must remove the chains before resuming normal travel. These requirements add to mandated rest periods and long working hours.
CDOT notes that these efforts by commercial drivers help keep roads open and ensure continued delivery of goods even during severe storms.
