Photo: Jeffrey Beall, CC BY 4.0, via Wikimedia Commons
Colorado’s Traction Law means that when CDOT activates it, your tires need at least 3/16 inch of tread and must be winter, all-weather or mud and snow rated, unless you carry chains or an approved traction device. AWD and 4WD vehicles comply if all four tires meet the tread depth. This guide covers the Traction and Chain Laws, I-70, and the mountain and winter rules in the Colorado Driver Handbook that new drivers need on the road and on the test.
Colorado Traction Law: what your car needs
CDOT can activate the Passenger Vehicle Traction Law on any state highway during winter storms or when conditions require it. When it is active, you need one of these:
- tires with at least 3/16 inch of tread that are winter tires (mountain-snowflake icon) or all-weather tires, or marked M+S or M/S
- chains or an approved alternative traction device
- AWD or 4WD, which CDOT’s FAQ says complies as long as all tires have at least 3/16 inch of tread
On I-70 between Morrison and Dotsero, CDOT says these rules apply from September 1 to May 31, or whenever conditions require.
Quick tread check
Measure with a tread depth gauge rather than guessing. CDOT advises against fitting just two winter tires: fit all four.
Colorado Chain Law for passenger vehicles
CDOT calls the Chain Law the final safety measure before a highway is closed. When it is active, every passenger vehicle must have chains or an approved alternative traction device, such as an approved cable chain or tire sock. AWD and good tires are not enough.
Fines for breaking the Traction or Chain Law
| Situation | Penalty (CDOT) |
|---|---|
| Not complying | $100 fine plus $33 surcharge |
| Not complying and causing a lane closure in one or more directions | $500 fine plus $157 surcharge |
CDOT’s FAQ says the Colorado State Patrol enforces these laws as secondary offenses, citing drivers who crash or cause traffic delays while not compliant.
How to know if the Traction Law is active
- highway signs
- COtrip.org, or call 511 for road and weather information
- CDOT text and email alerts (sign up through COtrip)
Mountain driving rules from the Colorado handbook
- Speed: unless posted otherwise, 20 mph on narrow, winding mountain highways and blind curves, and 40 mph on open mountain highways.
- Going down: shift to lower gears to control your speed on steep descents.
- Right of way: vehicles going uphill have the right of way over vehicles going downhill.
- Narrow mountain roads: if two vehicles meet where there is not room for both, the downhill vehicle backs up to a wider place or stops and leaves room, unless it is easier for the uphill vehicle to return to a turnout.
- Slow vehicles: if you struggle uphill, pull off at the first safe place or stay right so others can pass.
- Passing: it is illegal to use the oncoming lane near the crest of a hill, on a curve, or anywhere your view of oncoming traffic is blocked.
- Runaway truck ramps: never chain up, change a tire or park on the ramp or its entrance. Smoke from a truck’s brakes may mean it is out of control, so get out of its way.
Snow and ice: what the handbook tells you
- Roads are most hazardous when snow or ice begins to melt. Bridges, overpasses and shaded spots can be icy when other pavement is not.
- If you start to skid, take your feet off both the brake and the accelerator, then steer the front wheels where you want the car to go.
- With ABS, press the brake firmly and keep it pressed. Without ABS, use threshold braking, pressing just short of locking the wheels.
- 4WD helps traction, but it does not help you stop any sooner.
- Do not use cruise control on wet or icy roads.
- Clear all ice, snow and frost from every window before you drive, even for a short trip.
- Leave extra following distance and slow down.
Snowplows
- Plows and sanding trucks use flashing yellow and blue lights. Use extreme caution when approaching or passing them.
- It is illegal to pass a state, county or city plow working in tandem (staggered) formation with its lights on.
- Plows can create clouds of blowing snow that hide the plow itself.
Wildlife on Colorado roads
The handbook says about 90% of crashes with deer and elk happen between dusk and dawn. In marked animal crossings, slow down and scan. If an animal runs out, keep control of the car. Swerving hard can cause a worse crash than hitting the animal.
Scenario: Denver to the mountains on a snowy Saturday
- The night before, check COtrip.org for Traction or Chain Law alerts and closures on I-70.
- Check that all four tires have 3/16 inch of tread and an M+S or snowflake marking. If not, carry approved chains or socks.
- Pack food, water, warm clothes and blankets, as CDOT advises for winter trips.
- On the descent, use a lower gear rather than riding the brakes.
- Keep well back from plows and never pass a tandem formation.
Common questions
Is my AWD car legal under the Colorado Traction Law?
Yes, if all four tires have at least 3/16 inch of tread (CDOT FAQ). When the Chain Law is active, you need chains or an approved device anyway.
Are all-season tires OK?
Only if they are marked M+S or M/S, or are rated all-weather or winter, and have 3/16 inch of tread. Otherwise you need chains, an approved device, or AWD or 4WD with adequate tread.
Where does the Traction Law apply?
CDOT can apply it on any state highway. On I-70 from Morrison to Dotsero it applies from September 1 to May 31, or whenever conditions require.
What is the fine for the Traction Law in Colorado?
$100 plus a $33 surcharge, or $500 plus $157 if you cause a lane closure.
Who has the right of way on a steep mountain road?
The vehicle going uphill.
Should a learner drive I-70 in winter?
Practice on quieter snowy roads first with your supervisor. The Parent’s Supervised Driving Program encourages practice in rain, fog and snow.
Back to the Colorado learning to drive guide. Related: driving in snow, fog and rain, Colorado 50-hour log, Colorado teen license restrictions.
Sources
- Colorado Department of Transportation, “Passenger Vehicle Traction and Chain Laws” (codot.gov)
- Colorado Department of Transportation, “Winter Driving FAQs” (codot.gov)
- Colorado Department of Transportation, “Winter Driving” (codot.gov)
- Colorado Division of Motor Vehicles, “Colorado Driver Handbook” DR 2337 (12/05/24), Speed, Right-of-Way, Snow and Ice, Seasonal Driving, Mountain Driving, Emergencies (dmv.colorado.gov)
- Colorado Division of Motor Vehicles, “Mountain Driving” (dmv.colorado.gov)
- Colorado Division of Motor Vehicles, “Parent’s Supervised Driving Program” guide (dmv.colorado.gov)