It's been decided: this is March Mapness.
Here's the car-free commute map for Massachusetts. This shows the percentage of residents in each census tract who get to work on foot, bike, or transit -- anything that doesn't involve a car.
I'll be creating a map for each state and uploading census tract boundary files so that others who are interested can make their own maps showing whatever they'd like. If you'd like your state's map up earlier rather than later, just let me know.
Here's a link to the full-sized map.
For those interested in embedding the map on their own site, you'll want to go here, click the tab that says "Massachusetts," pull down the tab that says "Publish," and copy from there. The embedded map will show whatever you're looking at when you hit "Publish" -- in my case I was viewing Boston, for example -- so keep that in mind if you want to highlight a specific area.