I live in NY and I spent time living in the UK. In the UK most city centers had blocked off pedestrian areas that were only open in the morning for truck deliveries. This was possible because there was a commercial core where people did not reside, and there was plenty of outlying roads to park and drive around.
NYC has a LOT of people living in every area of the city. There is a lot of construction and residential deliveries, and emergency traffic. Certain areas have become pedestrian plazas, and some are closed off during the weekend but it is simply not possible to close off a significant amount of space. Anyone driving to Manhattan especially during peak times is not doing it out of convenience as it is extremely inconvenient to drive there. Often people have tools and equipment, and parking in garages in Midtown can easily cost you $40-$60.
If you live or are visiting NYC it is a nice thought to have pedestrian only roads. But we have to remember that the trades people that make city life possible really need roads to work.
With respect to emergency services, NYC ambulances and fire trucks get stuck in the traffic of private cars/taxis all of the time. If there were less cars, that wouldn't happen.
With respect to deliveries, if the sides of streets weren't given away to free parking, delivery vehicles would be free to use loading zones.
Most people don't advocate the removal of four-wheeled motor vehicles. They advocate the removal of private cars.
All these reasons were used in the UK too when pedestrian zones and congestion zones were first touted. For the most part, the envisioned Armageddon didn't occur.
In NYC I would expect the biggest problem would be the grid system. Closing off straight roads wouldn't really make a pedestrian nexus which is what makes these work.
Turning chunks of downtown pedestrian up to maybe TriBeCa would work fantastically well though.
NYC has a LOT of people living in every area of the city. There is a lot of construction and residential deliveries, and emergency traffic. Certain areas have become pedestrian plazas, and some are closed off during the weekend but it is simply not possible to close off a significant amount of space. Anyone driving to Manhattan especially during peak times is not doing it out of convenience as it is extremely inconvenient to drive there. Often people have tools and equipment, and parking in garages in Midtown can easily cost you $40-$60.
If you live or are visiting NYC it is a nice thought to have pedestrian only roads. But we have to remember that the trades people that make city life possible really need roads to work.