Let me take you back to Katrina and then to another hurricane that hit Houston. In Katrina, people who had no vehicles were stranded. Everyone in transport discussed and self flagelatted. A month later another hit in Houston. Everyone evacuated in their cars. Highways completely blocked at a standstill with backups for miles and miles. Everyone in transport discussed and debriefed.
The solution? Shared filled AVs will accommodate way more people — those who “own cars” and those who don’t. The system might be clever enough to use Waze or somesuch and reroute. Better still would be to have a city wide plan with emergency evacuation buddies where people starting in one neighborhood and seeking to go to a similar distant place would be in the same vehicle.