Winter Driving Sierra Chains: What to Carry

Caltrans enforces chain controls across Sierra mountain passes during snowstorms. When controls take effect, signs display the exact restriction level, and the maximum speed limit drops to 25 or 30 miles per hour. Highway checkpoints allow roughly 1 mile between the advance warning signs and the physical stop area.

Live traffic cameras along I-80 and US-50 across the Sierra crest.

Caltrans Chain Requirement Levels

California uses three official chain control levels under state law:

• Requirement 1 (R-1): Chains are required on all vehicles except passenger cars and light-duty trucks under 6,000 pounds gross weight fitted with snow tires on at least two drive wheels. Vehicles using snow tires must still carry chains. Trailers with brakes must run chains on at least one axle.
• Requirement 2 (R-2): Chains or traction devices are mandatory on all vehicles except four-wheel-drive or all-wheel-drive vehicles equipped with snow-tread tires on all 4 wheels. Every 4WD and AWD vehicle must carry chains in the vehicle.
• Requirement 3 (R-3): Chains are mandatory on all vehicles without exception.

R-1 and R-2 represent the most frequent conditions on Sierra routes like I-80 road conditions and US-50 road conditions. Caltrans typically closes a pass before posting an R-3 requirement. Under California Vehicle Code Section 558, legal snow-tread tires show "MS", "M/S", "M+S", or "MUD AND SNOW" stamped on the tire sidewall.

What to Carry in Your Vehicle

Carry tire traction devices sized to match your tire specifications. California law penalizes drivers who bypass checkpoints without required equipment; the California Highway Patrol issues citations and fines.

Stock these emergency and recovery items in your car:

• Proper-sized tire chains or traction devices in working order, plus chain repair links
• Flashlight and an extra vehicle key kept in your pocket
• Ice scraper or commercial de-icer spray
• Small broom to clear snow off windows, mirrors, lights, and license plates
• Shovel to dig out tires if the vehicle becomes snowed in
• Sand or burlap to regain traction if drive wheels spin
• Old towel for wiping hands and gear
• Concentrated windshield washer fluid formulated to resist freezing
• Potable water, food, warm blankets, and extra clothing layers
• Updated physical road map in case detours divert traffic off primary highways

Before departing, confirm that your tires are properly inflated with adequate tread depth. Inspect the vehicle radiator, belts, hoses, battery, defroster, heater, and exhaust system.

Where to Install Chains

Tire chains must go onto the vehicle's drive wheels. If driving a front-wheel-drive car, fit chains to the front tires; on rear-wheel-drive vehicles, fit them to the rear tires.

When highway warning signs dictate installation, do not stop in traffic lanes. Wait until you can pull completely off the roadway to the right side. Independent commercial chain installers work at official checkpoints; they are not Caltrans staff, are prohibited from renting or selling chains, and must provide a receipt with their badge number. When leaving a control zone, drive past the "End of Chain Control" signs to a designated pull-out before removing your devices.

Driving Rules Around Plows and Winter Traffic

Keep your gas tank full throughout mountain trips. A standard dry speed of 65 miles per hour is dangerous on packed ice and snow, which extend braking distances. Turn off cruise control on mountain grades, steer into slides if your tires break loose, and ease off the accelerator rather than slamming the brakes.

When following snow removal equipment:

• Stay back at least 4 car lengths behind plows and spreaders.
• Do not drive alongside a snowplow; blades hit snowbanks and shift sideways suddenly.
• Sand and cinder trucks spray abrasive materials across multiple highway lanes.
• If stuck in snow, crack a window for fresh air ventilation and keep the exhaust tailpipe clear of drifts to prevent carbon monoxide buildup.

For current Sierra pass reports, call the Caltrans Highway Information Network (CHIN) at 800-427-7623. In Nevada, dial 511 or call 1-877-NV-ROADS. You can monitor conditions before driving over mountain passes via the Road conditions hub, review SR-89 road conditions, or check the I-80 webcams at Donner Summit.