Riding along on a four lane, divided, limited access highway today jammin' to some ZZ Top (got to upgrade my speakers, though!). Waved at a pack of three or four bikes going the other way and the lead rider was patting the top of his helmet in an up and down motion while the rest just returned my wave. I passed a policeman on the shoulder but it was like 2 or 3 miles down the road. Is this the hand signal to warn other riders about the "law?" Never run across it before. Anyone know a good website/list of universal hand signals?