I don't know how you can stop these people. Dirty stupid pigs....... no, pigs are quite clean animals that insults pigs. Dirty stupid people.The one that really gets me is the road out of our village towards the town. About every metre, there is one of those Yakult yoghurt drink pots chucked into the verge. Someone who obviously worries about his (I'm guessing it's a he, but....) internal environment but doesn't give a hoot about the external one.
Councils don't make much of an effort to clean the litter up, unless you specifically report something.
There should be a campaign where litter is regularly picked up and the cost of cleaning made public, so people know the cost comes out of their pockets. try and make littering an anti-social act.