As a Metro train rolls along the tracks, who gets on and off? Where are they going? You can’t read minds, but thanks to Metro’s ridership data, you can watch patterns of riders on a typical train in a great new tool.

Morning peak riders at Union Station on a Shady Grove-bound Red Line train.

Image from

When public agencies release data sets, people can do all kinds of fascinating things with them. Yesterday, Matt Johnson used the Metro ridership data to show us which stations are busiest (with more to come), and Aaron Wiener looked at the most popular trips on different lines.

Reader Graham MacDonald sent along this interactive tool he created, Pick a train line, a direction, and a time of day, click play, and see a simulated train pick up and drop off passengers.

At each stop, the symbol for the train gets larger or smaller as the number of passengers on board changes. Meanwhile, circles at other stations on the map show where the passengers on the train are going.

Look below the map, and bar graphs show how the ridership of trains at this particular stop compare to equivalent stops along other lines.

It’s all aggregate data showing a typical train total numbers of riders along segments of the lines, not one actual train, but you can almost imagine the riders on board a train all going to their many destinations.

What interesting patterns do you notice from playing with this tool?

David Alpert is Founder and President of Greater Greater Washington and Executive Director of DC Sustainable Transportation (DCST). He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle. Unless otherwise noted, opinions in his GGWash posts are his and not the official views of GGWash or DCST.