I recently was visiting in the St. Louis, Missouri USA area.

I happened to be driving along Dorsett Road and realized that the traffic signs were directing me to cross under I 270 going the wrong way. But all the other traffic was doing likewise. I realized that I had just passed through a very unique intersection. When I got back to the hotel I looked it up.

It is a diverging diamond interchange completed recently. It is only the third or forth such intersection in USA. I checked osm and it still showed the original layout. So I fixed it. Its a pretty cool idea to relieve traffic congestion.

http://en.wikipedia.org/wiki/Diverging_diamond_interchange

http://www.270dorsettpage.com/