This might end up being more of a GIS question than a MASON question, but I hope someone here has dealt with this before.

I'm working on a model involving agents moving along an urban road system. My test case was DC, and it turns out that the DC road data on the city's website (http://1.usa.gov/1aei0L8) has the roads as polygons rather than lines. Is there a good technique or tool for turning polygonal road data into a network of linestrings?

Thanks!

-David