Those double ring ones like the illustration Tony Codfish posted confuse the heck out of me. They have them in DC and every corner there is a no turn sign. On our first visit, we could not figure out how to get out of the inner ring to the outer ring to make a turn. Went round and round and round, finally just did the turn. Got stopped and got a DC warning. Officer did not explain how to do it right, though. Must have been watching and waiting for us to give up and jump the signs. He was laughing of course. That was a while back, we were driving a big bad blue 70 Gremlin. It's hard to be sneaky in a car like that.