74, even if you could use rooftops in addition to parks etc, there would only be enough capacity for a small fraction of current urban populations. Single buildings on Manhattan have more people living in them than live in my entire town. SHTF plans for urban (and many suburban) areas can only be viable for short duration events. I realize that cities down South and out West are more spread out than what exists in the Northeast and that puts them in a somewhat better position than urban dwellers in the Northeast, and that many people live in single family homes, but how much food can you grow on those urban postage stamp sized yards? How many city folk have seeds and canning supplies, and the skills to grow and preserve food? Any long duration plan would have to include exiting the city.