They should make pedestrian-only streets in most dense places of Manhattan and use these money to improve public transportation. Even just a few blocks of no cars would make a huge difference for livability of the city center.
This is already underway
Big agree. Times Square would be a great place to start.
There's a large (long time) movement to do this to lower Manhattan, the most public transit connected area in the US (probably North America, definitely up there in the world). It's getting pick up again.