Three Laws, One Mountain Range
Colorado is the only state in the Mountain West with three separate chain and traction requirements, and confusing them costs truckers money and time every winter. Each law targets a different audience, triggers under different conditions, and carries its own penalties.
| Law | Who | When | Where | Penalty |
|---|---|---|---|---|
| Passenger Traction Law (Code 15/16) | Vehicles under 16,001 lbs | When activated by CDOT | I-70 mountain corridor, other passes | $100+ fine |
| CMV Chain Law | Vehicles 16,001+ lbs GVWR | When activated by CDOT | Primarily I-70 MP 133-259, other mountain highways | $100+ fine, up to $1,000+ for blocking roadway |
| Must Carry Law (2024) | CMVs 16,001+ lbs in commerce | September 1 through May 31 every year | 1,400+ miles of designated highway, 130 chain stations | $50+ fine plus surcharges |
The Passenger Traction Law (Code 15 and Code 16) applies to lighter vehicles and is not your concern as a CMV operator, but it affects traffic flow on the mountain corridor and you need to understand when it is active because it signals deteriorating conditions.
CMV Chain Law: When You Must Chain Up
The CMV Chain Law activates when CDOT determines conditions on mountain highways have deteriorated enough to require traction devices on commercial vehicles over 16,001 lbs GVWR. The primary zone is I-70 between MP 133 (Dotsero) and MP 259 (Morrison) — 126 miles of mountain highway. When activated, you must install chains on at least four drive wheel tires.
:::tip Check COTrip.org or call 511 before entering the mountains. Chain law status changes rapidly during storms. Once you are in the I-70 corridor, options for turning around are limited. :::
Approved Traction Devices
- Metal link tire chains conforming to SAE standards
- Tire cables
- AutoSocks (textile-based traction devices)
- Clip-on chains are PROHIBITED under all Colorado chain laws
Must Carry Law
The Must Carry Law requires every commercial motor vehicle 16,001 lbs and over operating in commerce to carry approved traction devices from September 1 through May 31 — regardless of whether chains are currently required. This applies across 1,400+ miles of designated highway served by 130 chain stations.
The distinction is critical: the CMV Chain Law tells you when to install chains. The Must Carry Law tells you to have them in the truck at all times during the season. You can be fined $50+ just for not carrying chains even on a clear day in October.
I-70 Chain Station Locations
Eastbound Stations
| Station | Mile Post | Notes |
|---|---|---|
| Dotsero | MP 133 | Western end of chain law zone |
| Wolcott | MP 157 | Before Vail |
| Vail Pass Bottom | MP 178 | Major chain-up area, recently expanded |
| Copper Mountain | MP 195 | Before Eisenhower Tunnel approach |
| Dillon | MP 205 | Last major area before tunnel |
| Loveland Pass Bottom | MP 216 | US-6 junction for hazmat |
| Georgetown | MP 228 | After tunnel, before steep descent |
| Dumont | MP 234 | Near weigh station |
| Idaho Springs | MP 240 | East of town |
Westbound Stations
| Station | Mile Post | Notes |
|---|---|---|
| Buffalo Overlook | MP 254 | Floyd Hill area, first chain area WB |
| Herman Gulch | MP 219 | Before tunnel approach |
| Eisenhower Tunnel | MP 213 | Tunnel area |
| Vail Pass | MP 179 | Summit area, expanded parking |
| Minturn | MP 171 | West side of Vail Pass |
| Eagle | MP 147 | Glenwood Canyon approach |
| Dotsero | MP 133 | Western end of chain law zone |
Other Mountain Pass Chain Stations
| Pass | Route | Elevation | Notes |
|---|---|---|---|
| Monarch Pass | US-50 | 11,312 ft | Chain stations at base east and west |
| Wolf Creek Pass | US-160 | 10,857 ft | Remote, steep grades, chain areas at both approaches |
| Berthoud Pass | US-40 | 11,307 ft | Near Winter Park, chain-up areas available |
| Fremont Pass | CO-91 | 11,318 ft | Near Leadville, limited chain areas |
| Red Mountain Pass | US-550 | 11,018 ft | NOT recommended for CMVs — steep, narrow, exposed |
Penalty Schedule
| Violation | Fine |
|---|---|
| Chain law non-compliance (no chains when required) | $100+ plus $32 surcharge |
| Blocking roadway due to non-compliance | Up to $1,000+ |
| Must Carry violation (not carrying chains Sept-May) | $50+ plus surcharges |
| Truck speeding in Glenwood Canyon | Double standard fine |
What This Means for Insurance
Chain law violations go on your record and affect your CSA scores. But the bigger insurance consideration is what happens when a truck without chains loses traction on Vail Pass or Floyd Hill. A loaded truck sliding on a mountain grade generates catastrophic claims — multi-vehicle pileups, guardrail damage, environmental cleanup, extended road closures. Colorado trucking insurance rates reflect this risk. Carriers running the I-70 corridor should carry $1,000,000 CSL minimum. The chain law exists because the mountain demands it. Your insurance should match.
Wyoming has a two-level chain law system that is simpler but equally important for carriers crossing between the two states on I-25 or I-80.
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