A
              |
--------------O-----O--------
       /      |      \
D      |      |      |      B
       \      |      /
--------O-----O--------------
              |
              C
O=traffic light

Traffic from A to B or C to D turns right and takes the U-turn. Traffic from D to A or B to C goes straight thru and takes the U-turn, then turns right. All other movements are standard. This is done to remove left turn conflicts, and is a variant on a jughandle.