That is way too cool Ned. Great idea I wonder what the costs would be to do the entire road system around the world and how would it work in earthquake prone areas?
The answer appears to be algae and Arizona is on the cutting edge to develop the technology. Here something to read from the Arizona republic today.
Unlike ethonal the use of algae has a net gain when processed. That mean more energy is produced then is used in the production od the fuel and it is co neutral so the tree hugers can't complain.
If it was engineered right, I'd think glass could be more durable than asphalt or concrete. I'd be more concerned about the electronics, but assuming the panels would be modular, at least they'd be relatively quick and easy to remove and replace.
I fear the infrastructure costs would be high enough to keep an idea like this from getting off the ground. Seems like a cool project, though. It'll be interesting to see if it gets off the ground.