“the road was only producing half of the expected energy” - great, so just 2 km of a solar road could power the streetlights of an entire city the size of Tourouvre, 3700 people.
We shouldn’t raise the white flag so quickly. I think we need a second iteration at least before we call it a failure.
Also I don't see how solar roads make any sense when there is so much unused roof space and parking lots. Putting panels over a parking lot is much easier since you don't have to build them to withstand many-tonne automobiles, they will always be in full sunlight instead of being covered by dirt and vehicles, and they can be angled towards the sun. Even in theory, I think solar roads are a failure.
In practice it will take many iterations to reach a point where it makes sense. Or it simply may never make sense.
The recent articles about some California farmlands being converted to solar fields does make sense. They were running out of water, but they had a lot of land to use for something.
Even if solar roads can work, there's still the problem of relatively inefficient tranfer of power over long distances. It makes little sense to spend a lot of money to make a solar road that's far away from energy consumers since a lot of the energy produced by the road will be lost in transit.
How about solar (covered) parking lots, solar roofs, etc. It makes far, far, far, far more sense.
Bitumen can also be patched and repaired relatively quickly and easily, and can use relatively simple machinery to repair/replace large sections at once. Solar panels require a lot more surface preparation, precision joining and when they break (because they will - accidents happen), leave dangerous road surfaces that cannot be easily patched/repaired.
Solar Roadways won't work with our current state of technology where we need fixed rigid panels. Something that is either a replacement for bitumen, or can be mixed into it and is able to self-assemble a current pathway might be a viable option. But we're a long ways off doing anything like that.
Regular roads don't fall apart in 18 months, they take 18 years (or longer) to do so.
Your county council evidently uses better contractors than mine!
More like 18 months in my region of the world.