It’s simply a waste of money if we can do the maths and see that it’s always going to be vastly worse than putting them on roofs, on gantries over roads, or literally almost anywhere else but on a dirty, flat surface with huge pressures on what we already knew were fragile and durable cells.
There are several factors, each alone that make this idea a non-starter. All these were known from previous experimental results so this never needed to be done. For example -
1. Placing cells flat reduces the power output by 30% over putting it at an angle and facing north. The angle varies with how far you are from the equator. So putting solar in roads will always yield at least 30% less power than putting it in an appropriate location.
2. Roads are extremely dirty. There’s dirt, brake dust, rubber, etc., not to mention shading from buildings, the natural geography and cars while they are driving over it. This will mean at least another 10-20% less power per solar cell, which will degrade as it gets dirtier. So you’re probably throwing up to 40% of your power away unless you’re cleaning them every week or so.
Then factor in damage, etc... a basic engineering assessment shows that it is infeasable, and even with massive improvements, rooftop solar and solar farms will always be correspondingly better.
But since you seem to be so big on experimentation, do you want to send me a few million dollars and we’ll put solar on the biggest area of all - the sea floor? Think of how much space there is! I mean, we can calculate that basically no light reaches it, but that’s not important, right? It’ll be valuable data!