What is the “Traction Law” and what are “Traction Devices”?

It is important to ensure that you have traction devices appropriate for winter driving conditions, snow-worthy tires or chains are not just for your safety, it is the rule of the road. Traction devices are required during severe winter weather conditions on roadways throughout Utah, including Big and Little Cottonwood Canyons.

AWD/4WD: M + S or M/S tires is the minimum requirement. Traction devices such as chains or 3 peak mountain snowflake (3PMSF) tires are also acceptable.

2WD: 3 peak mountain snow flake (3PMSF) tires (on all four tires) is the minimum requirement. Traction devices such as chains are also acceptable.


What is the actual rule?
The current Utah Administrative rule (Rule R920-6. Traction Device/Tire Chain Requirements) states that the Traction Law goes into effect when road conditions warrant, a decision made by UPD or UDOT. Per Utah code, 2/32 is the minimum tire tread depth needed for all roadways.
You know it’s going to snow, why aren’t you requiring traction devices in the morning before people go up?
It’s important to note that under the existing rule, requiring traction devices is based on current road conditions, not predicted conditions. When chains are installed and drive on dry roads, it can damage both the vehicles and the roadway. Having chains on when the roads are dry also makes it difficult for drivers to steer and travel at posted speed limits.
Why is the Traction Law taken in and out of effect throughout the day?
Restrictions are based on current road conditions. The Traction Law is put into effect as road conditions become difficult for motorists to navigate. Conditions can change by the hour in the mountains, and the Traction Law is not an uphill only rule. Drivers need to be prepared to go downhill during winter driving conditions, and prepared for changing conditions when they head uphill - even if it’s a bluebird day.
Why isn’t someone at the mouth every single time the Traction Law is in effect?
UDOT and UPD have to balance available resources and operational needs. Both agencies need to respond to in-canyon incidents and also have coverage areas beyond the canyons. UDOT and UPD reassess conditions and are actively assisting travelers throughout the day, regardless of conditions. Coordination is ongoing among these agencies to address staffing/resources to enable more frequent tire checks at the base.
So who is actually causing all these slide offs? I see an awful lot of 2WD vehicles with out of state plates heading up the canyons.
It’s true, plenty of out of state 2WD cars without traction devices make it up the canyons and slide off. However, many vehicles involved in slide offs or crashes are Utah residents who have met the criteria of the Traction Law and would have been allowed up. Poor tire tread for snow, driver difficulty in navigating winter conditions and speed also contribute to slide offs/cashes. It is critical that all travelers (even the locals) have confidence in their winter driving abilities. If you don’t, we recommend trying out the ski bus instead of white-knuckling it.
Snow tires are expensive, why should I buy some? What is the difference between those and M+S or M/S tires?
M+S and M/S tires are the same thing. Tire tread pattern is the only requirement for an M+S or M/S rating, while 3PMSF tires (snow tires) are required to meet performance standards on a snow-packed track that indicate improved traction and control in winter conditions. This is accomplished by a different rubber compound that provides more grip on snow and on cold pavement than an all-season tire.
So what good were the stickers you handed out at the beginning of the season?
The stickers we gave out this year mean that there are at least 5,000 vehicles properly equipped for driving in the canyons when traction devices are required. Additionally, when Traction Law is being enforced, vehicles with stickers move through these checkpoints quickly and help the overall flow of traffic.


UDOT wants you and your family to stay safe on the roads this winter. By following these tips and advice, you’ll be ready for winter driving. And don’t forget: Ice and Snow, Take it Slow!

You can open the PDF below to find winter driving tips in four areas:

  • Be Prepared
  • Be Aware
  • Be Cautious
  • Staying Safe Around Snowplows


Winter weather driving is challenging, especially in the Cottonwood Canyons. If you are visiting from out-of-town and renting a vehicle, check with the rental company to verify that your vehicle is equipped with four-wheel drive (4WD) or all-wheel drive (AWD) and the correct tires by showing them the Rental Car Tips PDF linked to below. 

To increase the amount of out-of-state visitors traveling in vehicles that are properly equipped for winter driving conditions, UDOT partnered with Enterprise Rent-A-Car, Alamo and National on the UDOT Cottonwood Canyons Sticker Program to inspect tires and distribute stickers to over 1,400 vehicles for the 2021/22 season.