I was just thinking the same thing. xD This is a totally useless idea (outside of Florida). If you wanted to harvest some energy reliably, there's plenty in wind and tides and ocean currents.
.35 W/m^2 vs 250 W/m^2 (after conversion losses) for solar, 2 solid orders of magnitude more energy. Even in cloudy conditions, solar is still going to deliver 15 W/m^2.
You'd be better off harnessing the power of wildlife to turn hamster wheels than spend money for the occasions to harvest a few joules when it rains. I imagine the operational costs and idle losses swamp any gains this system could ever hope to realize.
"Solar Roadways: When failure is worth 30 MILLION Dollars!"
"EEVblog 1534 - Solar Freakin' RAILways!"