Using data from the Metropolitan Transportation Authority, this animation tracks public transportation on a weekday, starting at 4am. Sumus, the Canadian software company behind these visualizations, uses the General Transit Feed Specification data from various cities to create a whole series of videos that you can check out on YouTube. Be sure to watch full screen in 720 HD to see the movement of subways and buses (which appear to be color-coded to match the corresponding lines).
For more videos from Sumus, visit the YouTube channel.
Via Kevin Allocca.