I needed to get home last night from Lake Tahoe along US-50 West. It was clear for several days when it started snowing.
Pretty much the only cars that were let through were 4WD or AWD. A chain installer set up shop just before the Caltrans checkpoint, and charged $20. There was about maybe an inch of snow on the road, and the white stuff was absolutely pouring down. On second though, I should have just turned back got a room in Tahoe, and call my boss in the morning.
At the checkpoint, the Caltrans inspector took a look at my car, checked the tires, and told me I was OK. The tires were Pirelli P Zero Nero M+S, and they were almost new.
I knew there might be snow, so I bought chains before I left. I bought them before I left so that I could try installing them once. They were also near impossible to find (in my size) in late March in the SF Bay Area; every gas station and drug store sells them along the route to Reno or Tahoe. At the checkpoint, when I asked about chains, I was told that every car has to carry them in those conditions, but I wasn't asked to show them.
I had my fogs on, and was crawling at anywhere between 15-25 MPH, and apparently it wasn't fast enough for some other drivers. A big SUV going in the other direction plowed into an embankement. I don't think anyone was hurt, but a Caltrans truck was helping the driver get out. I felt a little skittish at times on the all-seasons. If I lived in the area, I'd definitely get real snow tires. And after the snow stopped, I ran into some nasty fog and heavy rains, and other drivers still wouldn't slow down.