Every winter, a lot of people fly into Colorado, pick up a rental car, point it at the mountains and get turned around at the Eisenhower Tunnel. Not because they did anything reckless, but because nobody told them the state has a law about what your tires have to be, and the rental counter did not mention it.
This is the plain-English version. We drive these roads every day in winter, and the Traction Law is the single most common thing our passengers have never heard of.
What the Traction Law actually requires
When CDOT activates the Traction Law on a stretch of highway, every vehicle on that road must meet one of these:
- Four-wheel drive or all-wheel drive, with at least 3/16 inch of tread depth
- Snow tires (marked M+S, or with the mountain-snowflake symbol), with at least 3/16 inch of tread
- Chains or an approved alternative traction device
That is the whole test. Note what it does not say: it does not say “be careful”, and it does not say “use good judgment”. It is a vehicle-equipment requirement, and either your vehicle meets it or it does not.
Where and when it applies
CDOT activates it by segment, as conditions demand. In practice the stretches that matter to anyone heading for the high country are:
- I-70 west of Denver, particularly the climb to the Eisenhower Tunnel and over Vail Pass — the corridor for Summit County, Vail, Beaver Creek and the Glenwood route to Aspen
- US-40 over Berthoud Pass — the only real way to Winter Park
- Highway 82 up the Roaring Fork Valley into Aspen and Snowmass
- US-550 and Highway 62 over Dallas Divide — the Montrose approach to Telluride
- US-40 over Rabbit Ears Pass — the Steamboat Springs approach
From September 1 through May 31, the Traction Law is in effect on I-70 between Dotsero and Morrison at all times for commercial vehicles, and CDOT can activate it for passenger vehicles the moment it starts snowing. It frequently goes active with very little notice.
The Passenger Vehicle Chain Law is a step further
If conditions get worse, CDOT escalates from the Traction Law to the Passenger Vehicle Chain Law. At that point every vehicle, including four-wheel drive, needs chains or an approved alternative traction device. This is the last measure before a full closure.
If you hear “chain law” on the radio and you are in a rental with all-season tires, the trip is over for the day. There is no version of that where you continue.
What it costs to ignore it
The fines are real and they get worse if you cause a problem:
- Roughly $130 if you are simply on the road without the required equipment
- Roughly $650 if your vehicle blocks the highway as a result
The fine is rarely the actual cost, though. The actual cost is being turned around at Georgetown on a Friday night with a family in the car and a reservation in Breckenridge you are not going to make.
Why rental cars are the usual problem
This is the part that catches people, and it is not their fault.
A rental company at Denver International will happily give you a front-wheel-drive sedan on all-season tires in January. All-season tires are not snow tires. They do not carry the M+S marking or the mountain-snowflake symbol, and a front-wheel-drive sedan is not all-wheel drive. That vehicle does not satisfy the Traction Law, and nobody at the counter is obliged to tell you so.
If you are renting and driving yourself in winter, the questions to ask before you sign are specific: is this vehicle all-wheel drive, and what tires is it on. If the answer to the first is no and the second is “all-season”, ask to change vehicles. An SUV badge on the tailgate does not mean all-wheel drive.
What we do about it
Every vehicle in our fleet is all-wheel drive and shod for winter before the season starts. That is not a marketing line, it is the minimum required to operate legally on these roads in a storm, and it is why we can pick you up when a storm has already started.
Our drivers work this corridor in weather as routine rather than as an emergency. They carry chains, they watch CDOT before every run rather than at the trailhead, and they make the routing call on the morning of the trip based on what the roads are actually doing.
The honest argument for booking a driver in February is not comfort. It is that the person at the wheel has done the drive hundreds of times in exactly these conditions, and the vehicle is already compliant before you get in it.
How to check conditions yourself
cotrip.org is CDOT’s official source and the only one worth trusting. It shows live Traction Law and Chain Law status by segment, closures, and highway cameras you can look at before you commit to a drive. The COtrip Planner app carries the same data.
Check it the morning of your trip, not the night before. These activations change inside an hour.
Frequently asked questions
Do I need snow tires if I have all-wheel drive?
Not under the Traction Law — all-wheel drive with 3/16 inch of tread satisfies it on its own. Under the Chain Law, yes, you need chains regardless of drivetrain.
Are all-season tires the same as snow tires?
No, and this is the most common and most expensive misunderstanding. Snow tires carry an M+S marking or the mountain-snowflake symbol. All-season tires generally do not.
How much tread do I need?
At least 3/16 inch. A quarter inserted into the tread groove with Washington’s head down should touch the top of his head.
What happens if I get pulled over?
Roughly a $130 fine, more if your vehicle is blocking traffic, and you will be turned around. Enforcement at the tunnel approaches is routine, not occasional.
Does the Traction Law apply to my rental?
Yes. It applies to the vehicle on the road, not to who owns it.
Are your vehicles compliant?
Yes, always. All-wheel drive across the whole fleet, winter-ready before the season, chains carried.
If you would rather not think about any of this
That is most of what people are buying when they book us for a winter transfer. A compliant vehicle, a driver who has done the road in a storm, and somebody watching CDOT so you do not have to.
We run Denver to Aspen, Vail, Breckenridge, Keystone, Copper Mountain, Winter Park, Steamboat and Telluride all winter. Call or text (720) 967-9956.
Traction law is one of three things that stretch the winter drive to Denver. Departure times that account for all three are in How early to leave Aspen for a flight.