[maxerickson]

Asphalt roads are a type of concrete.

In my area, paved, minor county roads certainly don't have a Portland cement concrete base layer, when they are paving they might add some gravel during the surface preparation and grading, but that is about it. As you say, the ground movement shows through, and they are more susceptible to erosion.

[HeyLaughingBoy]

Here too. One of the gravel roads near me was recently paved and they simply flattened it, added some sort of cement + water spray (as opposed to the usual multiple inches thick layer of concrete) and the asphalt placed on top of that. It is definitely better than gravel, but it's already showing some wear in places.