Another strike against solar roads is that basically all year long you are driving on a surface that is pretty much an iced road, with variable grip on the surface. Any shading with rain makes it slippery, and different for each wheel as well. Then consider axle loading, here the legal maximum axle loading is 11 tons for each front steering axle, and 22 tons for any other axle on a HGV. Glass that will withstand 11 tons applied to the corner without chipping or breaking, especially when this point loading is applied at high speed, is both very expensive to produce, very thick ( you need a ground toughened glass with multiple internal laminated panels to have it be tough on the outside and thick enough to distribute the load) and you need to have the support structure be incredibly rigid to handle it. Might be 5 tons of steel and concrete for a single panel to handle this, basically making your road build equivalent to building the entire road structure as a ground laid bridge. Also going to require precision assembly, as any variation between panels will cause stress points and break tiles.
Compare this to a roof, existing support structure which already is rated for the extra mass, no need for any structural strength other than self support and wind/rail/snow/ice loading for the environment. Windows can easily be part of the system, as nobody has an entire roof comprised of glass window border to border, the power wiring is already there, the installation cost does not involve closing off existing streets to rip out hundreds of tons of existing roadbed to pour concrete, leave to cure for 28 days, then install a road bed back on them. Let again the efficiency of having panels that are aimed sunward to the most part, and running cooler due to being up where they can be cooled top and bottom by ambient air circulation.
Solar roadway is just a way to get profit for the companies laying them, all existing road builders who have a very vested interest in getting paid to replace an existing roadway long ahead of schedules lifetime, and then getting the never ending maintenance on the thing as well. Green credentials, and a massive profit as well, the investor return is impressive in having every person in the country pay them double the money they make in a year, every month from that lucrative contract, overrides all else from them.
Living in a country which is experiencing life with candles, because before we had electricity, and looking at the prospect of having to pay, per person, nearly $50k, because of poor decisions made in the last 9 years on corruption in the electricity industry, you are living in a dream world Nctnico. No ffed in tarrif here, but the local Wal mart has covered the entire shopping mall roof with solar panels, and the car park is fully shaded with solar panels to provide power, with around 32kW of inverters per corner they can put them. This they estimate is 30% of the power bill saved per store, and they are doing this to cut the expenses of the store. If it was sense to put the panels on the ground they would have done that during the store refresh, but instead they put them where they are the most cost effective and efficient instead. Instead they tarred the entire place after putting in the poles, and wash the panels to get that last bit of efficiency out of them.