I went to Oregon several years ago for the big eclipse. paid to spend the night with hundreds (thousands?) of people. Immediately after the eclipse people started roaring out of there. I decided to wait a while for the rush to be over. Big mistake.
When I left a few hours later it was bumper to bumper, stop and go - mostly stop for miles and miles and miles. I don't remember the time I left but it was early in the day. By the time it got dark it was still bumper to bumper and I was getting really tired. After a couple hours driving in the dark I managed to see a spot off the road that had space to pull into and get out of traffic. I slept in the car that night, but not well.
All night the traffic was like that and finally around mid-morning it began to clear out. It was still heavy for the next 50 miles or so, but at least it was moving.
This time I have a room reserved in Saint George Utah for the night before, on my side of the eclipse. I'll drive 40 miles or so into the area to see it from the road, then be the first one out of there when it's over. I hope there aren't too many thousands with the same idea. Saint George is outside the area, and there are still some rooms available there.