I've had many flats living in the "land of the goatheads." And as everybody has said it's rather gradual. Last summer on the Oregon Bike Ride I had a blow out where the tire blew apart in an L shape. The sound was so loud that I thought somebody had shot a gun. I screamed. A man riding beside me said, "Have you got a spare tube?" When I glanced back I said, "A tube won't do any good here!" I slowly braked. No problem, but I had to be SAGGED in. (It was sooo hot; I was glad!)