Throwing trash out or dropping off unwanted dogs or cats from a vehicle should be a moving violation with serious consequenses.
One thing I have discovered that seems to help a little is mow the right of way bordering the highway next to my property. Overgrown shoulders seem to be good spots to toss your garbage. Out of sight, out of mind I guess. If I have not had time to mow, when I get to it, the bush hog does a wonderful job of shredding plastic and aluminum containers and the occasional glass beer bottle. One would think that two and two would come to mind while dodging potential tire hazards left after I mowed and blew it out onto the road. But then those that litter don't have the brain capacity to put two and two together.