Speaking of corrugation; I always looked at them as an irritation until I nearly lost control of my car. I was driving on a paved road, and the pavement ended at an exit, on a curve, which I took a bit too fast. At the end of the exit, and beginning of the curve, was a nice washboard section. When my front wheels hit the washboard, they began to bounce, and I bounced into the left side of the road before they ended and I recovered control. Talk about a surprise; took me a minute to recover my cool.
I also saw a combine that was being roaded too fast, and as he exited a bridge, hit a big patch of washboard. The thing ended upside down in the ditch on the opposite side of the road.