greydead, you should actually post a thread for this one, I just happened by it.
By chance, that is one of my speciaties, but before providing you with all sorts of wonderful, and possible utterly useless solutions, let me first ask a couple of questions.
1 - Assuming a road surface, what type of road is it and what is the current usage?
2 - What would be the term of effectiveness you would be looking for?
3 - What kind of traffic volumes and types use the road?
4 - Most important, how much material is on the road to work with (gravels)?
You can email me direct or call me (via my little webpage) and I can provide you with some ideas.