Possibly with some nanotechnology materials they could become doable. But right now, nothing is tough enough, transparent enough and water-resistant enough to make them worthwhile. Even their "demo" on which no cars ever drove failed miserably. And what about when they break? You know, crevices, sinkholes, big trucks exceeding weight limits, dropping steel beams on them, etc. Then it's not just "patch the hole", it's "rebuild this complex machinery"!

Also, I think that in -40 degree weather, with blizzards going for days, the efficiency gets a little bit negated. Then at that point you have to use snow removal scrapers and calcium salts, which are corrosive at low temperatures... There are a whole slew of difficulties that aren't taken into account.

To me, that "invention" is simply pot smokers' delusions: it seems fine until you have to actually build it.