Oliver O’Brien of the University College of London has created a data visualization called “Tube Heartbeat” visualizing the flow of passengers on London’s underground rail network every 15 minutes during a typical weekday. The visualization is a time lapse depicting Tube ridership from 5:00 AM to 2:00 AM the following day, with different train lines and stations pulsing in size to reflect the varying number of riders, and arrows on the lines changing to show the dominant direction of travel. Users can select any of the 268 stations to see the number of riders that enter, exit, and transfer through the station in 15-minute intervals. Tube Heartbeat uses open data from the City of London’s Rolling Origin and Destination Survey, an annual survey of how rail passengers commute daily.