Car traffic has very different physics than that of people walking in a popular area. The flux of the number of vehicles, as you increase the number of vehicle

Car traffic has very different physics than that of people walking in a popular area. The flux of the number of vehicles, as you increase the number of vehicles on the road, starts out going up as one would expect. But at a certain point, adding more cars on a road starts slowing down the movement. And then as more cars come on the road, the flux goes down, there is less road capacity as it get more crowded. This is the fundamental diagram of traffic flow: https://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic_flow https://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic... So once cars on the road exceed that peak amount of flux, there's a phase change and cars start backing up. So with cars, gridlock really does mean that far far fewer people get serviced by a chunk of road. Whereas with people in a busy area, there really are more people there.