Mountain driving in the Sierra requires preparation before leaving. Conditions change rapidly, and chain controls are frequently enforced on high-mountain passes like I-80, US-50, and SR-431.
Chain Requirements Explained
When highway signs indicate chains are required, you must stop and install them. Failure to comply can result in a citation from the California Highway Patrol. You typically have about one mile between "Chains Required" signs and the checkpoint to pull over safely. Do not stop in active traffic lanes.
California uses three levels of chain requirements:
- Requirement 1 (R-1): Chains are required on all vehicles except passenger vehicles and light-duty trucks under 6,000 pounds gross weight equipped with snow tires on at least two drive wheels. Vehicles using snow tires must still carry chains. Trailers with brakes must have chains on at least one axle.
- Requirement 2 (R-2): Chains or traction devices are required on all vehicles except four-wheel/all-wheel drive vehicles with snow-tread tires on all four wheels. Even with 4WD/AWD, you must carry traction devices in the vehicle.
- Requirement 3 (R-3): Chains or traction devices are required on all vehicles, with no exceptions.
If you use a professional chain installer, get a receipt and note the installer's badge number. These installers are independent business people, not Caltrans employees, and they are not permitted to sell or rent chains.
Essential Gear to Carry
Before heading into the mountains, ensure your vehicle is prepared for winter conditions.
- Traction Devices: Carry chains that fit your specific tire size. Test them before you leave home to ensure they are in working order.
- Vehicle Maintenance: Check brakes, windshield wipers, defroster, heater, exhaust system, and battery. Ensure your tires have adequate tread.
- Fluids: Keep your gas tank full. Use concentrated windshield washer fluid to prevent icing on your windshield.
- Emergency Supplies: Pack a shovel, ice scraper, broom for clearing snow, sand or burlap for traction, warm blankets, extra clothing, water, and food. A flashlight and chain repair links are also recommended.
- Keys: Keep an extra car key in your pocket to avoid lockouts while installing chains or at ski areas.
Cameras on major Sierra mountain passes.
Driving Strategy
Speed limits are set for dry conditions. When snow or ice is present, reduce speed significantly. Stopping distances increase on slick surfaces. Avoid sudden braking, acceleration, or sharp turns.
- Snowplows: Stay at least four car lengths behind snowplows. Do not attempt to pass unless there is a safe, legal, and clear area to do so. Operators have restricted visibility and may be spreading sand or brine across multiple lanes.
- Bridges and Shady Spots: These areas freeze first. Exercise extra caution when crossing bridge decks or driving through shaded sections of highway.
- Stalls: If you become stalled, stay with your vehicle. Conserve fuel while maintaining warmth, and ensure your exhaust system remains clear of snow to prevent carbon monoxide buildup.
For real-time updates on road closures and chain controls, check the road conditions hub frequently. You can also monitor specific routes, such as I-80 road conditions, US-50 road conditions, or SR-431 Mt Rose road conditions, before and during your trip.
If you are unsure of current conditions, the Caltrans Highway Information Network (CHIN) provides updates at 800-427-7623. Official Caltrans QuickMap is the most accurate source for real-time traffic and chain control status.