For your interest and amusement, I found some really good rumble strips in Florida. They were ~3 inch discs, ~1 inch in height, glued into the middle of the right-hand paint stripe and appeared to be composed of small glass beads (like the paint stripe) glued into a matrix and put down at the same time as the stripe I think. A periodic break in their sequence every 20 feet or so would have been the only improvement I would want.
Ben Cowan
