Roof tiles would make a lot more sense. I think it's pretty easy to see that very little about the system makes any sense at all.
Even if the technology and economics were close to what would be viable, roof panels would still make a lot more sense. On a roof, you don't need to worrry about the surface neededing to hold weight, nor do you need to worry about the surface requiring traction.
I'm surprised nobody has brought up the legal impediments for roof solar. In my area (Atlanta) the building codes and the restrictions in nearly all HOA covenants explicitly forbid solar onstallations on roofs (for various reasons). This may date back to the days when roof solar meant hot water heating (either pool water or domestic ho water supply) when roof loading and leakage risk were the primary reason. The other mtoivation is esthetic, as a lot of the older technologies were fairly ugly!
Sharp used to have solar tiles, which I believe were to be used in place of typical asphalt shingles, rather than placed on top. Those dissappeared from their web site a few years ago. Now they are marketing "SunSnap" panels which have easier installation and integrated/available microinverters (EnPhase). http://www.sharpusa.com/SolarElectricity/SolarForResidential/SunSnap.aspx
@MHRackin....have a look at Crusty's links below, the tiles he links to are really quite good looking - not much different from roof slates. I know these are mostly used in the UK (from Welsh slate quarries) but there is no reason why the more usual roof tiles could not be built tlike this. In Australia a lot of roofs (mine included) use tiles - usually cement ones. A solar cell could be built into them without much trouble, I think?
@David Ashton: In most of the USA, the predominant roofing materials are shimgles. In my subdivision, that is literally the rule (HOA covenants). Even the color choices are limited to the ones originally offered by the developer. There have been allowances made for some new styles ("architectural" shingles that look a bit like tiles, with a 3D aspect) that were not around 15 years ago when development began. Tiles are mostly a Florida/California thing (Spanish-style barrel tiles). Even there that's mostly for up-scale houses.
I believe that you can also get "tiles" that look like cedar shake and possibly ones that have the look of the arcitectural asphalt shingles. It looks like you can get solar shingles tha tlook similar to the asphalt shingles but if the HOA is even specifying the colors that you are allowed to use, they porbably wouldn't pass (the pictures I saw they were significantly shinier than regular shingles)
Yet another reason to avoid neighborhoods with HOA covenants although it's getting harder to find...
Sanjib wrote, "the 'road' would get stolen if you do not keep guarding every 500 mtrs (or less) of the road!! How many guards you would need?"
Sanjib, that would be a problem in nearly every country. Keep in mind there are people in the U.S. who steal copper wiring because it's worth a few dollars. Imagine what stolen solar road panels would be worth to thieves!
I'm thinking that the best use for these materials is on roads / parking lots that get most of their use at night when there is no sunshine that would be shaded by the cars. They would also be best used in climates with lots of sun and little frost (in Connecticut we've not yet mastered paving roads with materials that can survive the winter). Finally, the segmented panels on highways will likely cause some road noise / resonance at high speeds that could be very annoying to drivers.
If the technology really works, is affordable, and is waterproof perhaps it should start being used on the rooftops of buildings and garages where the surface has continuous exposure to the sun and can avoid the stress of automobile traffic.
Regardless, it sounds like this will be feeding into the "grid" and not into batteries which would significantly increase the construction costs or inductive charging of cars (which would shade the tiles as they drove over.