A good road should last for tens of centuries. The Romans understood that, and engineered their roads accordingly. To blithely dismiss their roadbuilding expertise as consisting of "flat rocks" ignores the engineering underneath the road, described here. Or if you have kids, David Macauley's City may still hold up after nearly forty years.
American roads rarely last more than a few decades, unless consistently and constantly maintained. But they are comparatively cheap. I hear that European approaches tend to produce a more durable road, at greater expense.
That said, the solar roadway may not turn out to be a very good road by this metric, despite the added construction expense.