Roughly once a month I spend an hour or so picking litter from my woodland, mostly from the 300m verge next to the A24. Initially, when I was dealing with the backlog from many years of neglect, I would stop after I had filled 2 large bags, usually having reached about half way along the verge. I always litter pick south to north, so that I am facing the oncoming traffic. Although I am not actually on the road, I'm near enough to worry about people failing to stay on the road. Indeed, early on I have had to remove large parts of cars that were clearly the remnants of crash damage. Trees are a lot tougher than they look!
I've used different methods, my current kit is a high quality litter picker, waterproof gloves, and a litter picking hoop to hold the collection bag open.
Most of the litter is chucked out of passing cars. I don't really understand why they can't take it home, it feels like it's more effort to wind down the window and just chuck it out. And it's mostly food and drink - sandwich wrappers, cans, bottles etc.
But there are also more unusual items. The pic below shows a silencer box, found this month, It's about 500mm long, so not a trivial item to throw from a passing car, more likely something that fell off and got pushed to the side.
I've found a pair of trainers, an old boot (always useful when fishing) carrier bags full of I don't know what (didn't look) and a bookcase. The last is probably fly tipping, rather than littering, but it's all of a piece with people who somehow imagine that the world is full of magic tidy-uppers.
I'd really like to charge the fast food vendors for the mess they facilitate in my wood.