I got caught in a 25 mile traffic jam outside of Reno in 1993 or so.
It was between Christmas and New Years eve. I was at about mile 5 from the start of the jam and it was on I-80 at the NV/CA border. CDOT closed Donner Pass due to a supposed snowstorm that didn't happen. I sat in one spot for 13 hours before moving. I also got carbon monoxide poisoning because all the idiots were running thier cars all the time to run the heaters. I was sick for 2 weeks.
CDOT also mandated chains to cross the pass. So, I put the chains on. I got to the pass and it was clear with almost no snow or ice. So, I had to remove the chains in order to get down the back side of the mountain. Thanks, CDOT!
Mind you, there was no indication that the pass would close or that there was a snowstorm heading that way. It was an "advisory only" that a possible strom could happen, but no clouds and the radar map showed clear to the bay area. Sucked the whole way around.