For example, they don't know how much the panels for roadways will cost them. But the back of the envelope calculation (for just the glass) is around $60T. That's a hard number to work around. Even if that estimate is off by an order of magnitude, then that's still a ton more than we spend on roads.

Also, they state glass is tougher than asphalt. I don't think anyone was trying to argue that glass isn't harder than asphalt, but rather that given enough wear and tear, their glass panels will likely smooth out and reduce traction significantly. The onus is on them to prove that their surface will last with some legitimate road wear tests.

Finally, they point out that LED lighting is clearly visible in the direct sunlight... well, it is from a direct angle. Again, the onus is on them to show that their LED lane markers will be visible from a natural driver's perspective. More importantly, they'll have to show why it will be important to have dynamic markers on highways to begin with, and that they'll be as effective as existing strips.

Really, I don't think that they answered their critics in any sort of meaningful way. Solar roadways are a sexy idea, but not all that practical when you get down to it.