How will you keep the panels clean and how much power do you lose when they are dirty?
We had the opportunity to conduct a unique dirt test recently. Our drought conditions had become quite bad and everything on our property was covered in dirt/dust, including two identical solar panels that we have mounting on our roof. We decided to clean only one of them and then see how the outputs compared.
After one of the panels was cleaned,we monitored their performance throughout the day. It was sunny that day, and we learned that the clean panel produced less than 9-percent more power than the dirt covered panel. So even if we find that it's difficult to keep the panels clean, it may not be the issue many expect.
Most roads with high speed vehicles keep themselves pretty clean, as most small particles are blown off by the passing vehicles, with the exception of spills from oil, transmission fluid etc. There is a very common natural element called titanium dioxide, which turns substances like oil and grease into a powder that would be blown off by wind or washed away by rain. It's currently used on building facades to keep them clean. Spraying a road surface with titanium dioxide or a similar coating may solve the problem. Once we are able to hire a team (by meeting our goal on Indiegogo or working with an investor) we'll put some people to work on this very problem. Quite likely other solutions will be found that we haven't thought about just yet.
There will be some obvious obstacles such as oil spills, sandstorms, storm debris, etc. Here's the worst case scenario: if all else fails, we can replace snow plows with street sweepers where needed (vehicles with large rotating brushes). They're used here in Idaho in the spring to clear the roads of the sand that was used for traction during the winter months.