Ace, I work for a local government and know that we only use chip seal on already paved roads to extend the life of the road as you say. But I don't work on those projects, so have a question. It seems a chip seal over a dirt road would be extremely thin and unable to stand up to much traffic without the asphalt base. I would think it would just be broken up into oily gravel itself in a very short period defeating the purpose. Is this not the case?
It is (very) thin. That's why (in my opinion) I wouldn't consider it a paved surface. It is a thin layer of liquid binder (liquid asphalt) with very small "chips" (which you probably already know ); however, even that thin layer can last ten years or so. It will certainly depend on the base (rock) as all roads do, storm water management (nothing kills a road like water) and contour and traffic patterns. The chip seal creates a harder surface than the gravel road, and that greatly reduces water intrusion (increased life, reduced maintenance) and increases traction (increased safety and reduced maintenance). We've had really good luck with gravel roads that are well maintained. We added rock to the base and chip sealed them to reduce our annual costs greatly.