What planet do you live on where downtown in any large city can support the number of private vehicles that would be required to absorb the riders if mass trans

What planet do you live on where downtown in any large city can support the number of private vehicles that would be required to absorb the riders if mass transit went away? It's certainly not any major city I've ever been to. It's already literally faster to walk in midtown Manhattan than it is to drive (or, unfortunately, take the bus, since bus lanes are not well-policed enough to keep them moving quickly). I've lived in or spent a lot of time in many large cities in the US, and the only one I can think of where there's room for even a few more cars is Phoenix.