Don't carry on your back unless you have to.

Depending on your environment, you may consider carrying your BOB backpacks in a wheelbarrow, garden cart, or lashed to a handtruck or dolly. If you're on foot and most of your potential evacuation route is flat or paved, wheels could be a real back saver. If the going gets rough, ditch the wheels and strap the backpack on. Wheels could help with tired little feet as well.

This is just another view, it may not work in all situations, but it might make miles of walking a little easier. Sometimes it helps to approach problems an alternate way. Adapt & overcome.