''County engineering'' maybe that's why our back roads are in such rough shape? lol
600SL-
Crowning roads to the standard 1-4% is the best achieved drainage, gravel roads no matter where will need to eventually have the gravel re-machined with fines to create good compaction. Crowning the road with a standard ''A'' style slope you should have 1/2'' of rise for every 1' of width from the center or the drive..
As far as sloping vs Crowning goes it really all depends on water flow, if you are in a very hill like terrain where water flows in one direction then an in-slope or out-slope would be best suited, where a crowned road would be best suited in a more general application where proper ditching and drainage is available.
One last thing.. Compaction is key, without a solid base or proper compaction you'll be right back to square one in no time. I could go on about this stuff all day as I work in mining/road building.. but it's better to read for yourself, Hope this link gives you some insight to what you are looking for!.
http://www.dirtandgravel.psu.edu/resources/documents/crown_cs.pdf