I had a ride like that last year ... on my way from Beaverton, Ore. to Hood River, Ore.
We decided to take the "back roads." Only problem was, the map that we used didn't mention that after the road deteriorated badly ... or just how bad it would get.
We slowed down a bit as we progressed about 20 miles down a very poor asphalt road, which by the time the asphalt ended, had some truly massive potholes.
Upon encountering the dirt road however, the potholed asphalt didn't seem so bad. Another 10 miles or so down that road and we encounter was is effectively a 4x4 trail.
Again, neither the map nor the GPS had any indication of the present condition of this road.
We were faced with a bit of a predicament. Do we turn back the 30 or so VERY SLOW miles and find a detour, or do we push on as we are due to meet others in Hood River.
We pushed on. We did the outrigger trick as well over rocks, through deep ruts and the whole bit. Scraped the floor boards and underside many times, but we were only crawling along.
About 2 miles or so of the extremely rough dirt road and viola ... we get dumped onto a recently paved asphalt road!
All told, it took us about 4 hours to go a little over 100 miles on the "back roads."
I took the superslab back home that night