Coalition to Clean-Up Vacant Lots? Brady Campaign to Prevent Litter? According to a study done at the University of Pennsylvania, cleaning up vacant lots has a significant effect on people committing crimes using guns. I think it’s safe to say that, given this study, it shows cleaning up vacant lots has done more to reduce crime than anything advocates by gun control groups. So why not get on board? I mean, the goal is to reduce gun violence, right? Right!?!?