I have thought about this sort of thing in the past, the slowing to a stand still of traffic not arresting people, as an effective protest move. I live fairly close to NYC and hear the traffic reports everyday and it's bad with just normal traffic, I would think with a minimum number of people you could effectively shut NYC down due to all the bridges and tunnels. The taxi drivers have done it to an extent but they publicized it ahead of time and they were not really willing to loose their livelihood. Other groups might not be so easy to deal with or willing to be nice. Think of stolen tractor trailers disabled on three quarters of the main bridges in and out of the city it would be chaos and make worldwide news. To me it's all the more reason to avoid the place