The city zombies are dependent on “mass transit.”
Some prepare, some don’t.
You don’t think starving zombies know how to walk?
Once they got the idea that things weren’t going to come back they’d be on the hoof.
Millions of them. And not just the gang bangers. The socialites, marketing managers, school teachers, doctors, nurses, and the engineers needed to fix what got broken.
Once the cities burn to the ground the odds of fixing the infrastructure in less than a year get increasingly dicey. Especially if major roads are disrupted or destroyed.