Large megapolises like NYC need to start exploring the concept of 3D streets. Instead of having a single street level, on the ground, start building skyways between skyscrapers, where both cars and pedestrians can move. Take 45th Street. You could build a second street 20m above the ground, straddling the buildings on the eastern side of the street. You build ramps at both ends, and you build your aerial street through the buildings. This would require heavy modifications, if not outright reconstruction, of the buildings in question, but this is the way of the future for large, dense cities in this millenium. Our current approach to city design is primitive, and quite frankly medieval. We still build cities the way we built them in the Middle Ages: independent of one another, standing next to each other. But as NYC's traffic woes show, this is not enough anymore. If you want to reduce traffic in large cities, without restricting car ownership, then you need to make way for more cars.
Or you could go underground. But I don't know if that's a viable option in a city with a subway, and straddled by rivers. You would need to protect your underground highways from water infiltration. And you can't hollow the ground below your city too much, lest the millions of tons of steel and cement and glass above the ground start collapsing.
Tl;dr we need to start building Coruscant.