Interesting graphic for traffic flow

Tracking Taxi Flow Across the City
he New York Times gathered GPS data from taxi cabs collected from January-March 2009, and mapped all the pick-ups and drop offs--thus creating a heat map of the city's pulse.

What's more, the map has been plotted over the course of the week, and you can watch a time-lapse view that shows activity ebbing and flowing in different neighborhoods, depending on what's there. And you can also zoom in on eight select neighborhoods.