It never was, but the car problem always existed because roads needing to be clear for horses caused the same prohibitive issues of using streets for pedestrians.
> why do you think it would become true just by getting rid of cars?
It wouldn't be just getting rid of cars, its what you do with the space once you get rid of them. Added greenery, protected bike lanes, a lane or two for trains/buses, and you get a ton more pedestrian room. Suddenly people could want to be on the streets of midtown manhattan maybe, save tourist spots.
I suppose if you made say every 20th street open to one way single street traffic (so 20th goes west, 40th east, 60th west etc), and every even avenue open (2nd south, 4th north, 6th south), that could work
That said I don't believe a city without cars will work unless it's planned for that before building. Basically all everyday logistics would have to be underground. Obviously it would only work for very densely populated areas.
I'd like to see something like that though. Small densely populated areas connected by trains/metros and surrounded by forests.
We could say the industrial revolution was a great disaster as if disrupted how people worked, their relationship to labor, capital, etc., but it also enabled us to get where we are today.
Probably not what they are going for, but uptown was relatively undeveloped until surprisingly recently in historical terms.
Also there are lots of famous photos of kids playing on Manhattan streets from circa the '30s and earlier.
In London, building a new tunnel for crossrail involved threading a TBM through a gap with 80cm clearance (that's less than 2 cubits).
The deeper you go, the wider the problems above, the more existing infrastrucutre is effected, not to mention the issues of how to return to the surface.
Build decking over all the existing surface streets, only allow electric vehicles on the (current) underground streets, don't allow anything larger than a pushbike on the top.
What about all the businesses that occupied the old ground floor?
This multi layered fantasy seems to have been around since GM's world fair exhibit in 1939 at least [1], but I haven't seen it work.
[1]: https://en.wikipedia.org/wiki/Futurama_(New_York_World%27s_F...
I think that's a very hyperbolic prediction. I think elevating the automobile to the detriment of other forms of transportation will be viewed as a mistake, but the automobile itself is no more a mistake than the horse and carriage were.
> My dream is that one day most streets in Manhattan will be closed to car traffic and replaced with green space full of trees, flowers, children playing, and usable public space.
When was this ever true in Manhattan, and why do you think it would become true just by getting rid of cars? Crowded city streets predate cars by centuries.