80 miles - quite a journey? Yes and No. For some people, it would be very difficult or impossible. For experienced thru hikers, 80 miles would be less than three days journey over fairly easy terrain. I would seriously consider making a trip of that length on a bicycle, planning for about a day, perhaps two. The bike has some real advantages for evacuating - it can easily circumvent obstacles, and one can easily travel three times as far on a bike compared to foot travel, carrying equivalent weight.

Much depends upon circumstances and conditions, which will be fairly unknown when caught up in a disaster....