But I hadn't counted an another variable in the lifespan of an unpaved road, which is that although new roads are all paved, sometimes a disused paved road can deteriorate to the point where resurfacing it with gravel is more economical than repaving it. There aren't a lot of those kinds of roads, because it's generally even more economical to just shut the road entirely. But there are a few, and they account for nearly half the mileage of unpaved roads in my catalog.
Every time I go out scouting new roads for a rally there is a chance that I'll find a road like this. This weekend I found two, with a total length of almost two miles. And I can use them both on Essex. Wahoo!