When we were kids we blew off firecrackers at the police station door so they would chase us. That they did. Never caught us. Good practice for E&E training when I joined the army. Yeah, kids do stupid things, but this overpass thing never crossed out minds.
I’ve seen news stories where people were killed as thrown/dropped items passed through their windshields - in one case it was a bowling ball. What we have here in neighboring Newark NJ is tight fencing (small holes instead of the larger standard ones) on overpasses, and they arc backwards towards the sidewalk above, making it much more difficult for ferals to mess with the productive people going about their business.