Interesting. So, these were basically political favors to very small neighborhoods, just to give their driveway a route number?
Pretty much. The long answer is that, unique to the coal producing area of Appalachia, mostly WV and eastern KY, there is the issue of so-called "orphan roads". These are just roads that just developed in rural areas, built by the coal or gas companies, or just built over time by settlers, or whatever.
Lots of these became "county routes" in the 1960s, following a federal raid on abusive DOH practices, but that still left lots of people living on roads that did not show up on the map, so to speak. No legal way to maintain, as the DOT cannot spend money off the system. Leads to lots of issues (safety, who can drive there, school buses, ambulance/911, lots of things). Issue for many years. Underwood's idea was this HARP thing. The intention was good. He was talking about legitimate roads in rural areas that served a community.
Problem was it got abused in two ways. Lots of people, literally, got their driveway in the sytem (often named for themselves, BTW, I could have lived on Cook Road) and, in the more normal part of the state, lots of suburban tract housing became HARP roads. This was really just a sign, so NBD. But the main abuse, and it continues to this day, is now all of these HARP roads are in the state system and while the long ago promise was "as is maintainance", that is undefined, and if you know the right pol, you can get your driveway or your entire suburban tract housing development, paved.
Which, of course, takes money away from actual through highways.