The best Sierra powder days usually come with the worst Sierra driving. If it’s dumping at the resort, it’s probably dumping on Donner Summit or Echo Summit too, and Caltrans will have chain controls up. Knowing what each level means, and checking before you leave, is the difference between a powder day and four hours parked on I-80.
What R1, R2 and R3 mean
Caltrans posts chain controls in three levels:
- R1: chains, traction devices or snow tires are required on the drive axle of every vehicle, except four-wheel and all-wheel drive vehicles.
- R2: chains or traction devices are required on every vehicle, except four-wheel and all-wheel drive vehicles with snow tires on all four wheels.
- R3: chains or traction devices are required on every vehicle. No exceptions.
R2 is where most people get caught. An all-wheel drive car on all-season tires without the snowflake or M+S marking doesn’t qualify, so it needs chains. Carry chains that fit your tires even if you have four-wheel drive, because R3 applies to everyone and the CHP can turn you around at a checkpoint.
When the road is closed, no level applies. On I-80 over Donner Summit and US-50 over Echo Summit, closures happen in big storms and during spinouts, sometimes for hours.
The routes into each resort
- North Lake Tahoe and Truckee: I-80 over Donner Summit for Sugar Bowl, Boreal, Donner Ski Ranch and Tahoe Donner, then SR-89 to Palisades Tahoe and Homewood, or SR-267 to Northstar.
- The Nevada side: SR-267 and SR-28 to Diamond Peak, and the Mt. Rose Highway to Mt. Rose.
- South Lake Tahoe: US-50 over Echo Summit to Sierra at Tahoe and Heavenly, and SR-88 over Carson Pass to Kirkwood.
- The Eastern Sierra: US-395 to SR-203 for Mammoth Mountain, and the June Lake Loop on SR-158 for June Mountain.
Where to check
Each of these mountain pages on Ski Cams Live shows the current Caltrans chain control for its roads in the conditions panel, next to the resort’s own cams. For Mammoth, we also show the Caltrans road cams on SR-203 and US-395, so you can see the road itself.
Caltrans posts every control on QuickMap, and you can call 1-800-427-7623 for the same road report by phone.
A few habits that help
- Check twice. Look the night before to decide whether to go, then again before you leave. Controls go up and come down fast.
- Leave early, or late. The worst lines form at the checkpoints mid-morning on storm weekends. First chair, or a late start once the plows have caught up, beats sitting in the middle of it.
- Put chains on before you need them. Practice once in the driveway. Installing chains for the first time in the dark at a chain control is miserable.
- Fill up and pack for a wait. Water, snacks, a warm layer and a charged phone. If I-80 closes behind a spinout, you’ll be glad you did.
The cams are the last check. If the base area cams show cars parked under a foot of new snow and the parking lots filling, the roads will be busy. If the summit cams are in a whiteout, the upper lifts may be on wind hold anyway. Either way, you’ll know before you’re halfway up the hill.
