Crossing the Sierra Nevada in winter, heading to Lake Tahoe or Yosemite, the thing you're most likely to hit is chain control. This page reads Caltrans' chain control feed, updated every minute, and shows which roads need chains right now and at what level. Official road condition sites for the other western states are listed below.
California chain controls right now
Loading live data from Caltrans…
What R-1, R-2 and R-3 mean
Chain controls in a rental car
- Many rental contracts don't allow chains, or make you responsible for damage they cause. If you're heading into the mountains in winter, ask at pickup and check the car's drivetrain and tire markings.
- There's usually a checkpoint before the control area. Without chains or an exemption you'll be turned back. Roadside installers will fit chains for a fee you agree on.
- With chains on, the speed limit is usually 25 or 30 mph. On snowy days, check this page and the official map again before you set off.
Official road conditions in other states
| State | Data feed | |
|---|---|---|
| California (Caltrans QuickMap) | Live on this page | Open official site → |
| Nevada (NVroads 511) | Developer key required | Open official site → |
| Arizona (AZ511) | Developer key required | Open official site → |
| Utah (UDOT Traffic) | Developer key required | Open official site → |
| Oregon (TripCheck) | Developer key required | Open official site → |
| Washington (WSDOT) | Developer key required | Open official site → |
| Idaho (511) | Developer key required | Open official site → |
| Colorado (COtrip) | Not yet confirmed | Open official site → |
| New Mexico (NMRoads) | Not yet confirmed | Open official site → |
| Wyoming (WYDOT) | Not yet confirmed | Open official site → |
| Montana (511) | Not yet confirmed | Open official site → |
The 511 systems in Nevada, Arizona, Utah and Idaho and Washington's API all require a registered developer key or access code, so for now this page links to their official sites.
Data source
Chain control rules: Caltrans, dot.ca.gov/travel/winter-driving-tips/chain-controls. California chain controls: California Department of Transportation (Caltrans) CWWP2 public data, updated every minute and free to use. Your browser loads it directly from Caltrans. Conditions change fast; always follow official sites and road signs.