Following a link from the Low Dimensional Topology blog, I found this really interesting tidbit of information about a highway interchange in the US that has nontrivial structure. This particular interchange combines the American clover leaf pattern resulting from the standard right turn along a loop with the ‘British pattern’ of left turns. And the two sets are combined together in an interesting braided structure!
I wonder if this is just an accident of incremental design or if all architects sit down and think up such elegant structures. In any case, it sounds like this structure is going to be eliminated due to an incremental change to improve efficiency of traffic flows. That’s a shame!