"What if a person needs to bug out on foot and travel a great distance?"

First, be in shape and have good walking shoes. Be sure you have cash, bartering items, credit cards or equivalent as well as basics. Wehn this question comes up, I think of my wife's grandparents, who fled Moscow in 1920, traversing Siberia and winding up in Mongolia where my father-in-law was born. They traveled on foot, dog sleds, and train, among other ways. Sewing needles were hot items in trade for food through much of Siberia.

Remember,thru hikers on the big trails (PCT et al) can rack up 2000 miles in a single trip, although usually with some sort of support.