With 4.9 million in funding, about half from supporters though various crowd fundings, a plaza in Sandpoint, Idaho has been paved with 30 "road tiles" to power a nearby restroom and fountain. Nice idea, eh?
At $10,000 per panel, it would cost about $50 trillion to pave all of America's roads... just the panels, installation not included... probably another $150 trillion, more or less. You can monitor the daily power production here.
Wait... Un oh, the tiles produce under 1 kwh per day, in total. Enough to power the average microwave or hair dryer for a day. Far from what was hoped for. Well short of a single light or the restroom's power needs, but it'll get better as the sun moves north... maybe.
The tiles get some valid criticism though. I'm all for research, and I'm glad taxpayers are only "on the hook" for half of this (it seems) but even then, the project seems doomed from the start. Idaho = snow, trees, north. Not the best place, but typical of much of America. If it had succeeded there? It would likely have worked almost anywhere! (Except Alaska.)