I ride this trail for my commute. The Greenway is essentially a wide trench below street-level, with several bridges running over it. Originally built for freight trains, it's now been transformed into the Autobahn of MUPs. However, it does go through a crappy neighborhood.

A couple of summers ago someone dropped a chunk of wood off one of the bridges as I was riding by. Missed me by about 8 feet, but I turned off at the next off-ramp, went up to street level and doubled back to see if I could catch who did this. I came across two kids -- couldn't have been older than 10 or 11, crouching down behind the guardrail of the bridge. I couldn't really prove they did it, but I did manage to quite thoroughly scare the crap out of them.