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Colorado Traction Law, Explained for Visitors
What Colorado's traction law requires on I-70, when it applies, what it costs to ignore, and why all-wheel drive alone does not exempt your rental car.
Every year, thousands of visitors rent a car at Denver International Airport, drive west toward the ski resorts, and discover somewhere past Idaho Springs that Colorado has a law about tires. Usually they discover it from a state trooper, or from the back of a tow truck.
Here is what the law actually says, in plain terms.
When it applies
The traction law is in force September 1 through May 31, every year, on I-70 between Dotsero and Morrison. That is the mountain corridor — the stretch that carries almost every trip from Denver to Vail, Breckenridge, Keystone and Copper Mountain.
Note the dates. It starts on the first of September, when there is no snow anywhere and the aspens have not turned yet. The law does not wait for winter to look like winter.
The Colorado Department of Transportation can also impose it on any other highway in the state when conditions call for it.
What your vehicle needs
The requirement is about tires, not about drivetrain. Specifically:
- Snowflake-rated winter tires, all-weather tires, or M+S tires
- At least 3/16 inch of tread depth
If your tires do not meet that, you need chains or an approved traction device on at least two drive wheels.
The law applies to every passenger vehicle under 16,001 pounds GVWR. That includes four-wheel drive and all-wheel drive.
The most expensive misunderstanding
All-wheel drive alone does not satisfy the law.
This is the single most common mistake, and it is easy to see why. You rent an SUV, it says AWD on the tailgate, you assume you are covered. But the requirement is tread and rating. An all-wheel-drive crossover on worn all-season tires is not compliant, and the tunnel approach out of Silverthorne is exactly where that stops being a paperwork issue.
The law covers rental cars too, but the rental counter will not check your tires or raise the subject.
What it costs
| Situation | Fine | Surcharge | Total |
|---|---|---|---|
| Non-compliant vehicle | $100 | $33 | $133 |
| Non-compliant vehicle that blocks the highway | $500 | $157 | $657 |
The second row is the one that matters. When a car without proper tires spins out on a grade, it does not just stop that car — it stops the interstate. That is why the penalty jumps by a factor of five.
And the fine is the cheap part. Add the tow, the missed reservations, and the hours that everyone behind you spends stationary.
What this means for planning
If you are renting a car for a ski trip, ask the rental company directly whether the vehicle has winter or all-weather rated tires with adequate tread, and check them yourself in the lot. “It’s four-wheel drive” is not an answer to that question.
If that sounds like a lot of due diligence for a vacation, that is the honest argument for a private transfer: our vehicles are compliant for the entire season, and the tire question stops being yours.
Either way, the law does not care whether you knew about it. It starts September 1.
Related
- Denver to Vail car service — the route where this comes up most
- Ski resort transportation — resorts by elevation, with drive times
- Our fleet — vehicles and what fits in them