MileCheckHow do you drive safely in winter conditions?
Slow down more than feels necessary, leave five to six seconds to the car ahead, carry chains where the state requires them, and know your mile marker before anything goes wrong.
What is the chain law where I am driving?
It changes at the state line. The sign on the road and the DOT posting decide whether chains are required today. Our state pages state the law, the fine and the official source.
| State | The rule in one line |
|---|---|
| Washington | Four levels posted by pass and direction. Separately, vehicles over 10,000 lb must carry chains Nov. 1 to April 1. Ignoring a posted requirement is a $500 infraction. |
| Oregon | Posted by sign in snow zones. |
| California | R1, R2 and R3. Caltrans can close I-80 when conditions require it. |
| Colorado | Traction Law Sept. 1 to May 31 on I-70, plus a Passenger Vehicle Chain Law. |
| Idaho | Chain rule in Idaho Code 49-948 is for commercial vehicles. |
| Montana | Posted by sign. |
| Wyoming | Two chain law levels. |
| Utah | Traction devices can be required on designated roads. |
| Nevada | NRS 484D.515 and 484D.520. |
| British Columbia | Winter tires or chains on designated routes from Oct. 1. Ends March 31 on some routes and April 30 on passes and high-snowfall routes. Commercial vehicles have their own chain rules. |
| Arizona, New Mexico, Alaska | No chain-level system found. |
See chain laws by state for the index, how to put on tire chains, and the live chain control map.
How much following distance do I need on snow and ice?
AAA says to increase your following distance to five to six seconds. (AAA) TxDOT puts it as at least three times your normal following distance on snow or ice, and at least 200 feet behind a snowplow. (TxDOT) Michigan's highway safety office says it can take up to ten times longer to stop on snowy or icy roads. (Michigan OHSP)
How much farther does a car take to stop on snow?
CDOT published one set of numbers. From 60 mph on snow-covered pavement, a car on winter tires stops in 310 feet. On all-season tires without a mud-and-snow rating it takes 669 feet. On summer tires it takes more than 800 feet. (CDOT) A football field is 360 feet long. TxDOT's line is that speed limits are set for normal road and weather conditions, not winter ones. (TxDOT)
Do not use cruise control on any slippery surface. (AAA) Bridges, ramps, overpasses and shaded stretches freeze first. (TxDOT) Our page on black ice covers how to drive on it.
What should I carry in the car?
AAA's winter kit is a phone charger, a flashlight with spare batteries, reflective triangles, a first-aid kit, water and food for everyone in the car including pets, a traction aid such as sand or cat litter, an ice scraper and a shovel, and gloves, extra coats, hats and blankets. (AAA) Add tire chains that fit your tires and a full tank before the climb. Our winter prep checklist covers the car itself.
What do the words on the DOT report mean?
Pass reports use a short list of surface phrases. WSDOT does not publish a glossary, so these are the plain meanings as the reports use them. Bare and dry means pavement is visible and dry. Bare and wet means pavement is visible and wet, and water freezes whenever the surface drops below freezing, day or night. Snow and slush in places or ice in places means some stretches are covered and some are not. Compact snow and ice means the road is covered and packed hard. Treat it as ice.
The traction phrases are a different kind of statement. Traction tires advised is advice. The other three Washington levels are requirements. At traction tires required, passenger vehicles need approved traction tires. At chains required, 4WD and AWD vehicles are exempt only under the conditions in WAC 204-24-050, which include carrying chains. At chains required on all vehicles, they chain up too. (WSDOT) (WAC 204-24-050) California uses R1, R2 and R3, explained on our Donner Pass page. What "chains required" means covers the rest.
What does a plow on the map tell me?
Only where the truck is. The states and provinces that publish truck GPS are on our snowplow map shows each truck's last report with its route and mile marker. A parked truck keeps reporting from the yard. A truck that passed an hour ago says nothing about the road now. A pin is the vehicle's last reported position. It does not confirm that work is under way or what the surface is. Read the DOT condition report for that.
How do I slow down without losing it?
Brake before the curve, not in it. Keep steering inputs small. If the car starts to slide, ease off the pedals and steer where you want to go. Michigan's safety office puts the speed advice in four words. Drive slow on ice and snow. (Michigan OHSP) Pick a speed for the traction and visibility you have, not the posted limit. For scale, FHWA reports that freeway speeds drop 5 to 40 percent in heavy snow. (FHWA)
How do I report where I am if something goes wrong?
Give the dispatcher the highway, the direction and the mile marker. That is what 911, the state patrol and a tow company ask for, and it works where there is no address. The MileCheck app shows your nearest mile marker to one decimal, offline, and puts it on the CarPlay and Android Auto screen. Our guide to reporting your location on the highway has the script. If there is no signal, see how to reach help without a cell signal.
Which roads close most?
Read which highways are most dangerous in winter for the closure records state DOTs publish, and how do you know if a mountain pass is open for the official page in each state.
Know your mile marker before you need it
The mile marker works offline. Live DOT closures, chain reports, cameras and plow positions on your route are part of MileCheck Premium and need a connection to update. Runs on CarPlay and Android Auto.
Questions, answered
How much following distance do I need on snow and ice?
AAA says five to six seconds. TxDOT says at least three times your normal following distance, and at least 200 feet behind a snowplow. Both read October 2026.
How much longer does it take to stop on snow?
CDOT's figures from 60 mph on snow pavement are 310 feet on winter tires, 669 feet on all-season tires without a mud-and-snow rating, more than 800 feet on summer tires. Michigan's highway safety office says stopping on snow or ice can take up to ten times longer than on dry pavement.
Should I use cruise control in snow?
No. AAA says not to use cruise control on any slippery surface (AAA, read October 2026).
What should I keep in my car in winter?
AAA lists a phone charger, flashlight and batteries, reflective triangles, first-aid kit, water and food, a traction aid such as sand or cat litter, ice scraper and shovel, and gloves, coats, hats and blankets. Add chains where your state requires them.
What does compact snow and ice mean on a pass report?
The road surface is covered with packed snow and ice. Treat it as ice. Bare and wet means the pavement is visible and wet, and it freezes whenever the surface drops below freezing.
Does a snowplow on the map mean the road is clear?
No. A pin is the truck's last GPS report. A parked truck keeps reporting from the yard. Read the DOT condition report for the road surface.
What do I tell 911 if I crash on the highway?
The highway, your direction of travel and the nearest mile marker. The MileCheck app shows the mile marker offline.
Sources read October 15, 2026. Chain laws and fines change, and the official page is the record. The stopping distances are CDOT's published figures for one speed and surface, not a test of your car.