If equipping every roof in the Netherlands with solar panels would only supply 25% of demand, then (theoretically) wasting massive sums of money on very inefficient bike path panels is that much worse - such path panels won't make a dent at all.
> The approximately 140,000 km of roads in the Netherlands cover a total area of about 400-500 km2, which is significantly larger than the total (suitable) roof surface area.
The FAQ: http://www.solaroad.nl/en/faq/
(Btw, I wasn't the one who downvoted you.)
To me this is very questionable marketing non-sense. You take the excellent bicycling culture of the Netherlands, you combine it with solar energy and the result is profit.
Just exchange Wcycling track" with "landfill" and tell everybody you'd cover them for 300 times the normal price with solar panels and you'd be kicked in the balls.