Want to see how people move in and out of Metro stations? I made a Metro Activity animation using data from April 10, 2013. The data shows the numbers of entries and exits for each station in 15-minutes increments, from 4:45am to 1:00am (that’s 81 records).

WMATA has already visualized this same data set, in Visualization of Metrorail Station Activity. The date was picked because it had the 4th-highest ridership, with 871,000 trips, compared to 750,000 on an average weekday.

My goal for this new visualization was to design a tool that’s fluid and interactive. I used the HTML canvas element to create the animation. I can scale the canvas to fit the window. On top of each station, I draw an image that’s scaled to the data for that station. I can change the color and shape to indicate other values. A form on top shows the user controls.

Because there’s never one perfect way to visualize data, I wanted to let the user control how the data is displayed. The first choice is whether to show only the current 15-minute segment, or to let each new record get added to the total. The next control decides how the two data sets (entries and exits) are combined. “Imbalances” shows the difference between entries and exits. You can also control whether circles are solid or hollow, and the speed of the animation.

The design is a first-draft at this point. How could this tool be improved to make the underlying data easier to understand?

Update! I’ve added a few new features. A label will appear for a station when you move the mouse near it. By clicking the mouse, the map will zoom to that station. Clicking the same station, or away from the station, will return the zoom to show the entire system. And you can now see the exact numbers represented by the circles, using an option below “solid” and “hollow.” The slider has been modified so that you can easily manually set the time. To put it back into animation mode, change the “manual” setting to slow, medium, or fast.

Another update! The URL has been changed to accommodate a variety of data sets.

A Day of Metro, Entries and Exits

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