With all of the traveling we do, as much as 50 or 60 thousand miles each year -- I decided that picking up the garbage along the road would be a nice gesture, and would allow us the "right" to complain about the garbage that hasn't been picked up. Back when we first started this we lived along M-28 about 7 miles east of Marquette, and there'd be about five to ten bags of stuff each time we did a pickup. We learned that lots of the stuff we'd get was food - wrapper - related. Folks would buy their junk food and finish eating what they wanted of it and throw out the wrappers and napkins and french fries and so on. Ishta!
About seven years ago we moved to our present house, which is something like 20 miles south of Marquette on US 41. We get perhaps three or four bags of garbage at the very most when we pick up at the new location -- even though it's the same two-mile-long stretch that's normal for Adopt-a-Highway volunteers. We've decided that the smaller amount of garbage we get now is because folks finish their eating at least a few miles before they get to us, so they've already tossed out their food wrappers. We get lots of empty cigarette packages, quite a few bottles filled with fluids that we don't care to examine closely (!), and so on.
If you throw stuff out the window of your car -- even cigarette butts -- it is visible and does make the roads look less friendly, less inviting. Think about carrying and using a litter bag in your vehicle, please.