Made me think, what roads would actually be suitable for this?

They have to be:

1) cleaned often

2) have very little traffic

3) have a very large surface

And one of the solutions that pops up is: airport runways! They have a huge area, way larger than necessary to land a plane. The surface is always kept in good condition. The traffic is minimal, except for a few very busy airports. Some airports handle just a few planes a day, the rest of the time they stay unused, when they could've been producing energy instead.