Please do not spread that around. I want my bunkers to stay safe. Do not forget about Hwy 89 in your plans.
89 is pretty far out of the way. They’d have to cut east after St George. I-15 would be blown in the Virgin River Pass long before St George. So 89 should be fairly safe. There probably won’t be many moochers coming from the east to 89 because they’d have to make it through most of Arizona. I think the worst worry would be I-80 from Than Franthithco.
If you look at the maps you can see that even in our modern age that Utah is fairly isolated. Lots of land but not many highways in and out. And those highways mostly pass through canyons. The most moochers would come from the west and southwest.
This all just conjecture in fun, of course.