They state that their glass surface has been tested for traction... but I wonder how well it would operate when oil and exhaust are covering the surface, or rain, or ice and snow...
Asphalt seems to work well with the normal amount of oil/exaust grime buildup because it is fairly porous, and then oil kind of settles below the surface (until it rains).
The other concern is definitely the cost. It would be interesting to see it done in a small town for testing purposes. It would be nice if they stated the type of solar panels they are putting in these devices... Solar panels lose their effectiveness over time at a constant rate... The better types of solar panels in terms of longevity lose their effectiveness at a rate of about 0.5% per year... Other types of solar panels lose their effectiveness at rates of 1% per year or more.
I would guess these road solar panels could degrade even faster than that from wear and tear and all the scoff marks and scratches which would end up reducing the amount of light that is received from the panels.
I still think it would be a better idea to upgrade our nuclear power plants and create new state of the art nuclear facilities. I wouldn't be surprised if a state of the art nuclear energy facility would be more green than the amount of solar panels needed to match the amount of energy produced, as long as you take into account the greenhouse gases produced from manufacturing all of the solar panels required.
They meet all impact/load/traction requirements, and it destroyed/torn up a bit, its a fairly easy and quick repair. Each panel is an individual piece to the puzzle. So you can literally just pick up that piece and replace it with a new one. No need to get a whole road crew bring in heavy machinery, tear up the road, place down more cement, pave it out, wait for it to dry, etc etc. If one piece gets a little dent in it or crater (which is about the same likeliness as on current roadways), then how is it any different from your average day pothole?
If you can just pick up these panels off the ground, whats to stop someone from stealing all these road panels off the ground and parting them out for all the electronic metals and solar panels. Or whats to stop the semi truck in front of you kicking one of these up into the air when it drives down the highway going 70mph... Something tells me they would still be using cement underneath these things rather than just place them on loose dirt. We would still need road crews with heavy machinery to set and maintain whatever goes underneath these solar panels.
Also, the effects of mass producing a mass quantity of solar panels on top of what we already do could put a large chokehold on rare earth metals... Prices of electronics could skyrocket as a result, especially if one of our major suppliers of rare earth metals/minerals decides to no longer sell to us, or increase the price as supply drops.
"Thin, cheap solar panels need tellurium, which makes up a scant 0.0000001 percent of the earth’s crust, making it three times rarer than gold."
http://e360.yale.edu/feature/a_scarcity_of_rare_metals_is_hindering_green_technologies/2711/