MileCheckWhat do R1, R2 and R3 chain controls mean on I-80 over Donner Pass?
R1 means chains on every vehicle except cars and light trucks under 6,000 lb with snow tires on two drive wheels. R2 means chains or traction devices on everything except 4WD and AWD with snow tires on all four. R3 means chains on every vehicle, no exceptions.
Everyone exempt still has to carry chains. (Caltrans) On I-80 you rarely see R3. Caltrans says a highway will often close before R3 is imposed. Check the live chain reports on our California chain law page or the Donner Pass page before you leave.
What does each level require?
| Level | Who needs chains | Who is exempt |
|---|---|---|
| R1 | Every vehicle except the exempt group | Cars and light trucks under 6,000 lb gross with snow tires on at least two drive wheels. Must carry chains. |
| R2 | Every vehicle except the exempt group. Chains or traction devices. | 4WD and AWD with snow-tread tires on all four wheels. Must carry traction devices. |
| R3 | Every vehicle | No one |
Source: Caltrans chain controls. Vehicles towing trailers need chains on one drive axle, and trailers with brakes need chains on at least one axle.
How fast can I drive under chain control?
30 mph on I-80. 25 mph on US 50 and the other mountain routes. (Caltrans) Caltrans can also turn back any vehicle it judges unable to travel the chain control area safely. (Caltrans)
Why does I-80 close over Donner Pass?
Caltrans lists three reasons for temporary closures in the Sierra. Whiteout conditions, spinouts and avalanche control work. (Caltrans) Spinouts are the one drivers cause. One car without chains that slides sideways on the climb blocks a lane, and crews hold traffic until it is cleared.
When traffic is heavy in a major storm, crews may meter it, letting a limited number of cars onto the highway at a time. (Caltrans) CHP enforces chain controls and can cite and fine drivers who ignore them. (Caltrans) Caltrans does not list an amount, so we don't either.
Can I take a side road around chain control?
No. Caltrans tells drivers not to use GPS to bypass chain control or look for an alternate route. Side roads off I-80 and US 50 may not be plowed. (Caltrans)
What should I do before I drive Donner?
- Check the current level. Caltrans QuickMap or 1-800-427-7623. Our California chain law page reads the QuickMap feed every five minutes.
- Carry chains that fit your tires. Exempt at R1 or R2 still means carrying them.
- Use a pullout to chain up. Installers along I-80 are independent businesses, not Caltrans. Get a receipt and their badge number. They are not allowed to sell or rent chains. (Caltrans)
- Fuel up first. A hold can keep you on the road for hours. Auburn going east, Reno or Truckee going west.
In September 2026, before snow, MileCheck logged 128 events on I-80 in California, mostly construction. Winter counts go in our monthly road report. For when the Sierra season usually starts, see California seasonal closures.
See the chain level before you reach it
Your mile marker shows even offline. Caltrans QuickMap alerts on your route, chain controls included, and the nearest camera are part of MileCheck Premium and need a connection to update. Runs on CarPlay and Android Auto.
Questions, answered
What does R1 mean on I-80?
Chains are required on all vehicles except passenger vehicles and light trucks under 6,000 lb gross weight with snow tires on at least two drive wheels. Those vehicles must still carry chains.
What does R2 mean on I-80?
Chains or traction devices are required on all vehicles except four-wheel and all-wheel drive vehicles with snow-tread tires on all four wheels. Those vehicles must still carry traction devices.
What does R3 mean on I-80?
Chains or traction devices on every vehicle, with no exceptions. Caltrans says a highway will often be closed before R3 is imposed.
Why does I-80 close over Donner Pass?
Caltrans lists whiteout conditions, spinouts and avalanche control work as reasons for temporary closures in the Sierra. Spinouts and crashes on the climb are the most common. CHP and Caltrans hold traffic until lanes are clear.
How fast can I drive with chains on I-80?
Caltrans says the chain control speed limit is 30 mph on I-80 and 25 mph on US 50 and other mountain routes.
Can I use GPS to get around chain control on I-80?
No. Caltrans tells drivers not to use GPS to bypass chain control or find an alternate route, because side roads may not be plowed.
What is the fine for ignoring chain control in California?
Caltrans says drivers who ignore chain controls can be cited by the California Highway Patrol and fined. It does not list an amount.
Checked against Caltrans on October 15, 2026. Chain levels change by the hour, so check the live feed before you drive.