Using the river
People had limited options when they moved their families from the urban to the wilderness areas. Sure some people used covered wagons, that's the most common image I'll bet you imagine, but many also used flatboats and keelboats. The utilized the speed of a navigable river to use speed to move relatively quickly but also carry more items down river.
Flatboats were not very steerable, but they could carry a lot of tools, supplies, people, animals, etc. They didn't move fast at all, and were prone to river pirates as a result. There's no place to go if you're plodding along a river and short fast maneuverable canoes with ranged weapons come along side and then it's hand-to-hand. Then the pirates made off with womenfolk and a huge haul of goods. Some families today are descendants of them if you dig around in their skeleton closets. Other pirates whole growing clans were wiped out (including the captives and subsequent children) by incensed townsfolk and survivors who'd formed posses.
[link to mjcpl.org
[link to www.essortment.com
Keelboats used poles and bigger crews to steers the rivers. Many had very large cargo holds and actually had cannon.
[link to www.greatriverroad.com
It's very possible that smart folks might use the lesser considered routes of rivers to extricate themselves from a urban area by small watercraft. Many are available like pontoon boats, canoes, rowboats, john boats, etc. Of course using the river's current and stealth, one could quietly slip away, then fire up engines as long as possible and move great distances. But then one would have to be very prepared on what to do, precisely planning the escape, and then where's the final destination and how to then move all the cargo?
I think it's a doable plan versus taking a car that can get tied up in traffic. It's something to consider carefully in any event as others may use the same strategy as Big and Little Harp did so long ago. Inevitably post-collapse, the first trade networks will again happen as river traffic.