Looks like for once I made the right choice: yesterday after the eclipse I launched directly out of Mackay, Idaho, and headed south on 26/84. The traffic was heavy, but not so much so that it stopped things from moving at highway speeds and I managed to get home in about 4 hours. I didn’t take the shorter I-15 route because I figured it’d be swamped. I later heard that other folks who *did* take I-15 made decent time; it wasn’t too busy.
It looks like what happened was that everyone in eastern Idaho also assumed that I-15 yesterday would be a nightmare and decided to wait till today to head south. With the result that I-15 became the parking lot the media had promised, just a day late.
Note that the northbound lane is *empty.*