If you call the Yosemite roads hotline (209-372-0200 – then press 1 and 1 again) in the winter, you may hear the operator mention various “R” code requirements for different roads.
Here’s what they mean:
R0: No restrictions.
R1: Tire chains or traction devices required unless you have snow tires.
R2: Tire chains or traction devices required unless you have snow tires and 4-wheel/all-wheel drive.
R3: Tire chains or traction devices required on all vehicles.
Any time chain controls are in effect, Federal law requires all vehicles to carry chains, even if they have snow tires or 4-wheel drive and the current chain requirements are only R1.
You should expect to carry chains from November through March.