If you travel in town a lot you'll find this fascinating. And possibly it'll explain a few late arrivals.

Oliver O’Brien, a researcher at UCL, took data published by Transport for London (TfL) and created a remarkable analysis of the city's over-subscribed underground railways. TfL recorded the exact number of people exiting and entering tube stations every 15 minutes to build a map of the daily journeys of the city’s millions of commuters.

To my mind this is where the web excels, an amazing piece of work. I originally saw this on Wired magazine's terrific website.