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Traction Law Checker

Will your car meet the traction and chain laws on your trip? Pick the states you are driving through, enter the car and its tires, and see if it meets each level of each state’s law, from the Cottonwood Canyons to I-70, and what to buy or carry if it falls short.

Where are you driving?Pick every state on your trip. Each one has its own rules.
We read the drivetrain and weight rating from the VIN. Nothing else is looked up.
or enter it yourself
1

How it drives

DrivetrainLook up the VIN above and we fill this in. Otherwise, your owner’s manual or the badge on the back will tell you.
Gross vehicle weight ratingIt is on the sticker in the driver’s door jamb, marked GVWR. Every car and SUV, and nearly every pickup, is under 12,000 lbs.
2

The tires on it now

What is marked on the sidewall of all four tires?Look near the tire size. All four have to carry the marking. How to read your tires
Tread depth on the most worn tireUtah’s Cottonwood Canyons need at least 5/32 inch, and Colorado and Nevada need 3/16 inch, which is 6/32. A new tire usually starts around 10/32 or 11/32.
3

What you carry

Do you carry chains or another traction device that fits your tires?Chains, cables, snow socks and studded tires all count as traction devices.

Heading into the mountains?

See live cameras, closures and traction and chain law status for Utah’s ski canyons and Colorado’s I-70 corridor before you go.

Check Road Conditions

Level by level

Answer the questions above and the breakdown builds here.

Pick a drivetrain and a tire type to see the breakdown.

How to read your tires

The two markings that matter, and how to check your tread.
3PMSF, the mountain with a snowflake

Three-peak mountain snowflake. The tire passed a snow traction test, so it counts on its own in every state here, even on a front- or rear-wheel drive car. True winter tires carry it, and so do “all-weather” tires. Most all-season tires do not.

M+S, M/S or M&S

Mud and snow. It describes the tread pattern, not a snow test, and many ordinary all-season tires carry it. In Utah it counts only on an AWD or 4WD vehicle. Colorado accepts it on any car with enough tread, and in Wyoming it counts at Level 2 on an all-wheel drive.

  • Check all four. The rule is about the tires on every wheel, so a mismatched spare or one odd tire can fail you.
  • Measuring tread: a tread depth gauge costs a few dollars at any parts store and reads in 32nds of an inch. Measure the most worn spot on the most worn tire. Utah’s Cottonwoods need 5/32 and Colorado needs 6/32 (3/16 inch). Our DIY kit includes one.
  • The quarter test is not enough here. If you can see the top of Washington’s head with a quarter upside down in the tread, you are near 4/32, which is already too low for the Cottonwoods and for Colorado. A quarter cannot prove you have enough.
  • Not sure? Any tire shop will check the markings and tread for free, and during the season many do it as part of UDOT’s Cottonwood Canyons sticker program.

When and where each state’s law applies

Which roads, when it switches on, and what happens if you are stopped.

Utah

  • Class III, the Cottonwood Canyons: Big Cottonwood (SR-190) and Little Cottonwood (SR-210), the roads to Alta, Snowbird, Brighton and Solitude. Same rules as Class II, plus at least 5/32 inch of tread. Officers check at the mouths of both canyons when the traction lights are flashing.
  • Class II, the Traction Law: other designated mountain routes, such as those around Park City, Ogden Valley and Sundance. See UDOT’s route map.
  • Class I: only vehicles over 12,000 lbs gross weight have to chain up. Cars, SUVs and ordinary pickups are not affected.
  • It can start before the snow. Since the 2025 changes, UDOT can switch the law on up to 24 hours before a storm arrives.
  • If you do not comply: you are turned around, and you can be ticketed. It is an infraction with a fine of up to $750.

Colorado

  • Traction Law (Code 15): in effect on I-70 from Dotsero to Morrison every year from September 1 to May 31, and on any state highway when CDOT posts it. Since fall 2025 the tires decide it, not the drivetrain: winter, all-weather or M+S tires with at least 3/16 inch of tread, or chains or an approved traction device.
  • Passenger Vehicle Chain Law (Code 16): called in severe storms as the last step before a closure. Every car needs chains or an approved traction device, AWD included.
  • Fines: $100 plus a $33 surcharge, or $500 plus a $157 surcharge if your car blocks a lane.
  • Commercial vehicles follow CDOT’s commercial chain law, which is not covered here.

Nevada

  • “Chains or snow tires required”: cars under 10,000 lbs need snow tires or chains. A snow tire carries the M+S or mountain-snowflake marking and has at least 3/16 inch of tread.
  • “Chains required, except”: every vehicle chains up except four-wheel drive with four snow tires.
  • The Tahoe roads, like Mt. Rose Highway, Kingsbury Grade and US-50 over Spooner Summit, allow only 4WD or AWD with snow tires, or cars with chains, when controls are up.
  • Over 10,000 lbs: chains on the drive wheels at either level.

Wyoming

  • Level 1, hazardous conditions: travel is limited to cars with chains, adequate snow tires, or all-wheel drive.
  • Level 2, extremely hazardous: limited to cars with chains, or all-wheel drive with mud and snow or all-weather tires. A two-wheel drive car needs chains. Commercial vehicles chain at least two drive wheels.
  • Where: WYDOT posts it on mountain routes such as Teton Pass and South Pass when conditions call for it.
  • Fines: $250, or $750 if the violation causes a highway closure.

Idaho and Montana

  • Idaho: the chain law covers commercial vehicles over 26,000 lbs on I-90 (Lookout and Fourth of July passes) and US-12 (Lolo Pass). There is no traction law for passenger cars. Studded tires are banned from May 1 to September 30.
  • Montana: chains are required for vehicles towing a trailer on signed passes, such as Homestake, Bozeman Hill and Marias, when the signs flash. There is no traction law for passenger cars. Studded tires are allowed from October 1 to May 31.
  • Either way, plan for snow: these passes get serious winter weather, so winter tires and a set of chains in the car are wise even when nothing is required.

Shopping for a car that can handle the mountains?

We help buyers find the right car, check it over and negotiate the price, so you end up with something that suits your winters and your budget.

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Verified October 2026. These rules come from each state’s transportation department and statutes for the 2026-27 season. The state, highway patrol and local police decide when and where the law is in force, and an officer can turn back any vehicle they judge unsafe even if it meets the rule. This is general guidance, not legal advice. Sources: