Computer programmer Andrew Walker has created fascinating data visualizations of mass transit patterns in a 24-hour period for 40 of the world's major cities. These visualizations are based on publicly available General Transit Feed Specification (GTFS) data made available by transit authorities. Google uses GTFS data for transit schedules.
New York City: 24 Hours of Mass Transit Activity
For similar videos of many other cities including San Francisco, Los Angeles, Boston, Washington D.C., Chicago and many more see the full article and STLTransit YouTube Channel.