I'll leave the ideas for providing solar power to the homeless to the otherwise homeless troll who is living in mom's basement to debate and comment on...

However, the idea of capping freeways with arrays of solar panels is not that far fetched, and even has been considered in several places, and the same has been suggested for rail lines (as this is a "rail" chat board), locations like the Goldline/210 Freeway in the trench through Pasadena have even been proposed. These would be way bigger spaces, but not unlike what you are seeing in parking lot solar installations, larger scale, that's all.

The use of "air rights" over freeways and rail lines has been proposed for other uses as well. Like a proposed park over the Hollywood Freeway trench, between Santa Monica and Hollywood Blvd, that would be way cheaper to build, than buying urban land for park space in that area. Air rights over part of the Goldline ROW in Pasadena were reportedly sold a few years back, but nothing has gone up over the tracks, as of yet.

Solar is not going to generate off peak hydrogen like wind to power those "evil" non "wired" ZEV Stadler Flirt's...

But, what solar does seem to do best, (by the time of day production charts) is to mostly provide a good sized afternoon "bump" in power for "peak" air conditioning demands, and of course to recharge batteries for off peak use and load balancing.

You have to learn a lot about electrical generation and power outputs when you do things like RR electrification studies, and are looking at funding some of these EV demonstration projects.