You have an excellent point there, but the costs are unfortunately way too high to be feasible, not even remotely. And you have to consider how - in places whe

You have an excellent point there, but the costs are unfortunately way too high to be feasible, not even remotely. And you have to consider how - in places where there is snow - you have to choose to either forfeit the (possibly little) energy the panels can produce in winter or anyway clean them from the snow anyway. The good ol' rule of the thumb is that (of course it depends on the country) the cost is 10,000,000 Euro's per km of highway (plain, mainly earthworks), 20,000,000 per km on bridges/viaducts, 30,000,000 per km in tunnels. (the "base" price may of course vary, but the relative proportions remain roughly valid) An artifical tunnel or sbow shed, besides the solar panels, would be probably 1.5 to 1.7 times the cost of the "simple" highway.