Imagine if, in high density areas like Manhattan, cars were simply not allowed. Wow. The thought of how pleasant Manhattan would become if only cabs + busses + delivery trucks + ambulances were allowed makes me almost too happy. Would be so awesome.
I just don't understand this. I moved to Manhattan last year, and while there some things I've been annoyed about, it wouldn't have occurred to me to put "cars" on that list. I didn't bring my car here, and having driven a rental a couple times in the city, it's hard for me to imagine why anyone drives here if they don't have to: the experience as a driver is far, far worse than as a pedestrian.
Look at some of “urban plazas” [1] that have replaced short sections of road and witness how much more peaceful and open the city can feel when roads are removed in favor of people. Or, go down to 14th St. I was there this past week and it was wonderful—so much quieter and more open, and buses were moving smoothly.
[1] http://www.nyc.gov/html/dot/downloads/pdf/list-of-plazas.pdf