Map of highway signs

This is a fun map by Matt Dzugan. Search for a city, and see the segments of highway in the United States that are headed that way:

I set up thousands of queries to Google Maps, asking for directions from Point A to Point B and parsed its responses, looking for the text toward ___, signs for __, and ramp to ___.

This enabled me to build a database of all the segments of road that are listed as heading towards various cities.