Seasonal · Winter Driving

Chain Control and Winter Mountain Passes: Driving the West Safely

What each chain-control sign means, how California, Colorado, Washington, Oregon and Nevada differ, the rental-car clause that catches people out, and where to stop before a pass.

9 min read5 states compared6-step chain practiceUpdated November 2026

The checkpoint at Donner Summit doesn't care that your SUV says AWD on the tailgate. Under chain control in California, a vehicle that looks perfectly capable can still be turned around because it lacks the right tires or chains for the posted level. The same is true, with different wording, in Colorado, Washington, Oregon and Nevada. The penalty is a fine and a long wait; the real cost is a ruined schedule and, occasionally, a night in your car. This guide explains what each sign means, compares the five western states side by side, covers the rental-car clause most guides ignore, and shows how to plan around storms instead of sitting in them.

Quick answer

California chain control has three levels: R1 requires chains or snow tires on the drive axle, R2 requires chains on all vehicles except 4WD/AWD with snow tires on all four wheels, and R3 requires chains on every vehicle. Carry chains even with AWD.

Key facts

Colorado's Code 15 accepts AWD with adequate tires; Code 16 requires chains or approved traction devices
Many rental agreements prohibit chains, and chain damage is often excluded from coverage
Rent an AWD with snow-rated tires, or rent in a mountain market like Reno or Denver
Stop on the near side of the pass: Auburn before Donner Summit, Idaho Springs before the Eisenhower Tunnel
Cross the next morning, after plows have cleared the road

California Chain Control: R1, R2, R3

Level	What it requires	AWD/4WD exemption
R1	Chains, traction devices or snow-tread tires on the drive axle	AWD/4WD exempt if tires qualify
R2	Chains required on the drive axle of all vehicles	Exempt only with snow-tread tires on all four wheels, and chains must still be carried
R3	Chains required on all vehicles, no exceptions	None

R3 is typically posted just before a highway closes, and speed with chains is limited to 30 mph or less. Roadside installers charge roughly $30–$70 to put chains on (as of 2026, cash is common) and less to take them off. Always check Caltrans QuickMap before you leave and again at the last town before the pass.

Cable chains vs link chains

Cable chains are lighter and fit tighter wheel wells but wear out faster. Many newer cars with low clearance list approved chain types in the owner's manual; check yours, because the wrong type can damage a brake line or fender.

Colorado, Washington, Oregon and Nevada at a Glance

State	Law	What it means	Where to check
Colorado	Passenger Vehicle Traction Law (Code 15) and Chain Law (Code 16)	Code 15: AWD/4WD or winter-rated tires with at least 3/16" tread, or chains. Code 16: chains or approved alternate traction devices required. I-70 mountain corridor rules apply roughly Sept 1–May 31.	COtrip.org
Washington	Traction tire and chain requirements on posted passes	Snoqualmie, Stevens and White passes post requirements; AWD is often permitted when signed, but chains are required when posted for all vehicles.	WSDOT pass reports
Oregon	Chains required or traction tires	Signs say 'chains required' with exceptions for approved traction tires on lighter vehicles, depending on level.	TripCheck
Nevada	Chain controls on Sierra passes	Mt. Rose Highway and US-50 post chain requirements similar to California's.	NDOT 511

Fines vary and change

Colorado fines for violating the traction law start around $130 and can exceed $650 if you block a lane and cause a closure. Rules and amounts change, so verify each state's current rule on its DOT site before you go.

Tires 101: M+S, Snowflake and What the Law Actually Accepts

Two sidewall markings matter. M+S (mud and snow) is a manufacturer's self-declared label that most all-season tires carry; it says little about winter performance. The three-peak mountain snowflake (3PMSF) symbol means the tire passed a standardized snow-traction test. In several states, including Colorado and Washington, the snowflake tire is the safest way to satisfy traction rules without chains.

Tire type	Marking	Typical legal status	Real-world snow grip
All-season	M+S only	Accepted under R1 in California; often not enough under R2	Fair on packed snow, poor on ice
Winter / snow tire	3PMSF snowflake	Accepted under most traction laws	Good on snow and ice
Summer or performance	No M+S	Not accepted when snow rules apply	Dangerous below 45°F
All-terrain	Often M+S, some 3PMSF	Check the sidewall	Good in deep snow, varies

Tread depth matters too. Colorado's traction law specifies at least 3/16 inch of tread. The quarter test (insert a quarter upside down in the groove; if the top of Washington's head is fully visible, you are below 4/32 inch) is a rough check, but 3/16 inch is 6/32, so a tire that barely passes the quarter test still falls short of Colorado's rule. A $10 tread-depth gauge removes the guesswork before a winter trip.

Reading Road Conditions Before You Leave

The best chain-control strategy is knowing before you get to the pass. Use the state's own source, because they update before aggregator apps do.

State	Source	What to look for
California	Caltrans QuickMap	Chain-control level, closure status, live cameras at the summit
Colorado	COtrip.org	Traction Law and Chain Law codes, Eisenhower Tunnel status, I-70 incidents
Washington	WSDOT pass reports	Snoqualmie, Stevens, White: requirements, delays, closures
Oregon	TripCheck	Chain requirements, cameras on Cascades passes
Nevada	NDOT 511	Sierra pass controls, I-80 and US-50 conditions

Check three times

Check the night before to decide whether to go, the morning of to decide your departure time, and at the last town before the pass to decide whether to cross. Conditions can change in two hours, and the third check is the one that saves you from sitting in a closure.

If You Get Stuck in a Closure

Closures on Donner Summit and I-70 can last four to twelve hours. Most are an inconvenience; a few become emergencies. Preparation is mostly about not panicking.

Stay with your vehicle. It is shelter, visible to plows and rescue crews, and easier to find than a person on foot.
Run the engine about 10 minutes each hour for heat, and keep the tailpipe clear of snow to prevent carbon monoxide from entering the cabin.
Conserve fuel. This is why the half-tank rule exists: if you are stuck for six hours, you need the fuel.
Use blankets and layers first, then the engine. Dress in layers you can add or remove without getting damp.
Keep your phone charged with a power bank and share your location with someone before you leave.
Call 911 only for emergencies, and use the state's road-condition line for updates on reopening.

The Rental Car Problem Most Guides Miss

What most guides miss

Many major rental agreements prohibit installing chains, and damage caused by chains is typically excluded from coverage. Your 'I'll just rent chains at the pass' plan may violate your contract.

Rent AWD with 3-peak-mountain-snowflake tires and confirm tire type at the counter, not on the website.
Rent from a mountain market like Reno or Denver, where fleets often carry snow-rated tires.
Ask whether chains are allowed and have it noted on your contract.
Time the trip around storms so you never need them.

Shop snow chains at REI →

Practice Before You Need It

Fit the chains once in a dry driveway. It can take 20 minutes the first time and under 10 after practice.
Pack the helpers: waterproof gloves, a kneeling pad, a headlamp and a trash bag to kneel on.
Identify your drive axle (front for most sedans and crossovers, rear for trucks).
Install on the drive wheels, lay chains flat, drape over the tire, connect the inside, then the outside, then tension.
Drive 30 feet, stop and retighten. Chains loosen after the first roll.
Drive at 30 mph or less and remove them as soon as the road is clear to avoid damage.

Counterintuitive

The best time to learn chains is a 50°F afternoon at home, not a 20°F roadside shoulder in the dark with traffic passing at 40 mph.

Stop Before the Pass: Overnight Strategy

When a storm is forecast, stop on the near side of the pass and cross the next morning after plows have run. You trade an extra night's hotel for a clear road and a full tank of patience. Good staging towns:

Pass	Highway	Stop in
Donner Summit	I-80	Auburn or Colfax (before the climb)
Echo Summit	US-50	Placerville
Eisenhower Tunnel	I-70	Idaho Springs or Georgetown
Snoqualmie Pass	I-90	North Bend

Find hotels in Auburn, CA →

TripsGalaxy.com plans your route with overnight stops before the big passes, so a storm becomes an early dinner rather than a closed highway. Plan it free →

The Winter Car Kit Checklist

Chains sized to your tires, plus the install helpers above.
Winter washer fluid rated to -20°F. Summer fluid freezes on the windshield.
A collapsible shovel (about 2 lbs) for digging out of a plow berm.
A wool blanket, water and snacks for at least 4 hours of waiting in a closure.
Half-tank rule: never go below half a tank in the mountains in winter.

For the full kit, see our road trip car kit guide, and for the Tahoe-specific drive, see our Lake Tahoe winter guide.

Common Questions

What do R1, R2 and R3 mean in California?+

R1 requires chains or snow tires on the drive axle. R2 requires chains on all vehicles except 4WD/AWD with snow tires on all four wheels. R3 requires chains on every vehicle with no exceptions.

Do I need chains if I have AWD?+

In California you must carry chains even with AWD, and you must install them under R3 or if your tires aren't snow-rated during R2. Colorado's traction law accepts AWD with adequate tires under Code 15, but Code 16 requires chains or approved traction devices.

Can I put chains on a rental car?+

Many rental agreements prohibit chains, and chain damage is often excluded from coverage. Ask the counter for an AWD with snow-rated tires, or rent in a mountain market like Reno or Denver where fleets are equipped.

What should I do if a storm hits before a mountain pass?+

Stop on the near side of the pass, in towns like Auburn before Donner Summit or Idaho Springs before the Eisenhower Tunnel, and cross the next morning after plows have cleared the road.

Continue Reading

Seasonal Guide

7 Best Winter Road Trips in the US: Routes That Are Better in the Cold

7 US road trips that are genuinely better in winter — Death Valley, the Natchez Trace, Florida Keys, Big Bend, and more with gear tips.

Read Guide

Gear Guide

Road Trip Car Kit: Everything Your Vehicle Needs Before a Long Drive

14 car kit essentials and a 5-point pre-trip vehicle check — the road trip preparation guide for the vehicle, not the suitcase.

Read Guide

Planning & Advice

Altitude Sickness on a Road Trip: Prevent It

How to drive Colorado and Wyoming's high country without altitude sickness, with a sleeping-altitude plan and warning signs.

Read Guide

See Your Trip Come to Life

MIZA AI instantly turns inspiration into a fully mapped, day-by-day itinerary. Here's a sneak peek.

Generated by MIZA AI 5 Days