Re: IS the road doctor in
There's a strip of township road around the corner of a T-intersection in the middle of a mild slope that does the same thing. For what it's worth, the township with road graders, dozers and dump trucks hasn't solved the problem either. They grade it down, the wash-board is back in a few weeks. They spread gravel, it comes back. They scrape the gravel off grading it some more, it's back. More gravel, and so on.
It seems to be a mystery, and I suspect that Gordon is right, changing the base and the drainage would solve the problem. However, money for that much work probably isn't in the Roads Budget. Besides, us locals know enough to slow down around that corner. Guess it's a problem for everyone else though.
Around here, gravel means glacier deposit. It's a mixture of sand and small rock. The amount of sand and the size of rock depend on which pit it comes from. The stuff packs well, and the sand washes out. A decent layer of rock is left on the surface. Once packed, the surface is pretty durable and fairly erosion resistant. That's what's on my drives, and it hasn't wash boarded or required much maintenance. I did put 4" flex drain over the side in several places where some erosion started. I used the same stuff to build up a pad for our construction trailer.
What I grew up calling gravel, or pea gravel, is called crushed rock here. Crushed rock doesn't pack well and it doesn't freeze solid. In general, it's not very desirable stuff to have on a drive, especially if a blower or blade is used for snow removal.
We've got plenty of glacier deposit here, and it's used for maintaining highway shoulders and fills. It does seriously erode in some areas where there are no drains. Maintenance crews just fill in the erosion channels with more gravel. I notice that they have started using ground asphalt some places. It doesn't look that the ground asphalt is much more durable than plain gravel. It seems erodes around and under the asphalt.