I think the best thing to do is put down a good base, pack it and then put your gravel on top...

if it's a public road, call the county. if it's a private road i agree with RuthieG. around here we use railroad slag or steel mill slag for the base. holds in good. just make sure it's smooth or it will be forever rough.

Even if you have a good underlayer, eventually you will have to regrade a hardpack road. A blade works, but if not properly used can make matters worse, tearing up the road. A york rake works very well for light regrading and smoothing. I have both a york rake and a rearblade for my 30hp Kubota. Tried once to use the rearblade on some fresh hardpack I'd just had delivered. Went right back to the york rake. I groom my 500 ft or so of steep drive once or twice a year, depending on how bad the manure trucks tear it up.

narcnh

We re grade ours at least once a year, it washes when we have real heavy downpours.

What is railroad slag?

I wondered what slag was too. I have never heard of it before.

We have almost a quarter of a mile of gravel road....about a third of that length tips down from the county road to our low-water bridge and the rest tips up through the pasture to our house. We have gotten some really serious washes in the uphill portion from time to time due to the large area that sends runoff that way. We put large creek gravel into the very deep portions with some smaller stuff to fill in between the big chunks and then have what is called locally "dirty rock" over it all. The dirty rock is one inch limestone with a LOT of limestone dust along with it. When that is well packed it provides a surface that is almost "concrete like".

We have that delivered, in a truck with a barrel in the middle(so we get the rock we need in the tracks). We usually ask the dump truck driver to run over it a few times and then drive over it numerous times ourselves to pack it down.....the longer you have to pack it before the next big, washing rain the better it holds.

We have also had some "dirt work" done to provide a fairly wide, gentle swale (to divert runoff before it gets to our road) along side the uphill road that gives some protection without "ditching" which in this hilly area causes ugly gashes to occur from erosion. Then, we seeded with fescue (which develops an enormous root system) and strawed heavily to help it get a start. There are still some small trouble areas along but we try to address those by placing heavier straw (sometimes have used whole bales) to form barriers to slow water flow and catch any soil that is moved downhill. Believe that we will be able to get it all sodded within a couple of years....it has been two years since we had the dozer in.

I smooth off our farm lanes with dragging tires. We have some heavy implement (front-end loader) tires that we use as feeders. We have cut the sidewalls back to prevent any hoof catching. Keep the hay out of the mud, from blowing away.
I just run a short chain behind the tractor to tire, then second, pretty short chain to second big tire. Drag where I want things smoothed out. Old tires are often free, better than tractor tires. My horses were THROWING the smaller tractor tires around!! One horse hooks his hoof on the cut edge of these bigger tires, drags them a bit, NEVER picks them up to move. I DON'T have to hunt for the tires now when feeding.
Our lanes are gravel, fairly flat, but get chewed up with horses and tractor/spreader going thru on wet days. Large heavy tires seem to smooth things up pretty well. Chain allows some sideways movement of tires, aiding in smoothing the ruts. I try to drag when dirt is damp, not mucky, easy to even out.
Though I will drag to smooth out the deep mud of spring, removes slop and standing water in paddocks, aids in drying top dirt up quicker. However the underneath mud takes much longer to dry with just a smooth top.
I have a chain harrow, which is nice to drag with, excellent for deep mud in paddocks, drying it out with small furrows. Can be used smooth side down too, for smoothing off, just not heavy enough for my clay soil, like the big tires. Teeth down will just tear up your good packed surfaces more, not what I want for the driveways, lane.
Tires are best for smoothing or dragging for drying things out fast.

sorry, should have actually said "railroad cinders" but we always called it slag. makes a heck of a base. slag is actually the term for the leftovers of making steel. which also makes a good base

I have a 35 hp tractor and a couple miles of gravel and
dirt roads on my ranch that I have to maintain. About five
years ago I was spending about $1,500 a year just on buying
more gravel. Well a freind of mind told me about a grader that would sovle all my problems and would prevent me from
having to buy any more gravel because it resurfaces the gravel and pulls it away from the ditches putting a nice crown on my roadways so I bought me one and I can tell you
this I would't recomened anything but one of these units.
It is called Dura-Grader and it has performed just the way
my friend told me it would saving me alot of time, and money. I think the website address is
www.dura-grader.com check it out and let me know what you
think

Here is a link that might be useful: Dura-Grader website