Chain Laws in Colorado
Quick answer: Colorado has a chain or traction law that applies when signs or the state DOT activate it. CDOT activates the Traction Law during winter storms or when conditions require, on any state highway. On I-70 between Morrison and Dotsero it can be enforced with fines from 1 September to 31 May. The Chain Law is the last step before a closure: every vehicle then needs chains or an approved alternative traction device. Today: Season on: applies when CDOT activates it (1 Sep to 31 May).
The rule
CDOT activates the Traction Law during winter storms or when conditions require, on any state highway. On I-70 between Morrison and Dotsero it can be enforced with fines from 1 September to 31 May. The Chain Law is the last step before a closure: every vehicle then needs chains or an approved alternative traction device.
Tires that qualify
Under the Traction Law: tires with at least 3/16 inch tread that are winter tires, or marked mountain-snowflake, M+S or M/S, or all-weather; or chains or an approved alternative traction device. CDOT strongly recommends 4WD or AWD in the mountains.
Snow chains
Required on every vehicle when the Chain Law is in force.
Studded tires
Not confirmed. Check the official source below.
Fine
USD 100 plus a USD 33 surcharge; USD 500 plus a USD 157 surcharge if your vehicle blocks a travel lane.
Tips for visiting drivers
Rental cars must meet the Traction Law too: check the tread (3/16 inch) and the tire markings before you head up I-70.
Official source and last check
Colorado Department of Transportation (CDOT): Traction Law and Chain Law · Official text, cited · last checked
Also checked: COtrip (live road conditions)
Not confirmed on an official page: studs. We show "Not confirmed" rather than guess.
This is general information, not legal advice. Rules change and local signs always apply; check the official source before you travel. "Right now" is worked out from today's date and the dates above; where the rule depends on snow, ice or signs, it applies only when those are present.