A highway interchange that allows vehicles to change from one roadway to the other without requiring any left turns or crossings. Seen from the traffic chopper, it resembles a four leafed clover.
Sometimes they came with electronic
signs that light up with the words "TOO FAST
" if you take the turn at excessive speed
. You don't see these much anymore, probably because people thought it was a challenge
Not me, of course. Ahem.