A comprehensive google KML file of over 1,700 roundabouts in the USA & Canada with slider data when each roundabout was constructed (roughly). Roundabout data subdivided by size (single lane, double lane, tripple lane, and mini-roundabouts). This took quite a while to put together and most of the data was taken from Kittelson's roundabout database.
Let me know what you think. Thanks
http://www.mediafire.com/?77yqodwcczt4fc8 (http://www.mediafire.com/?77yqodwcczt4fc8)