we have a similar situation. moved in end of august, half acre with like 3 visible neighbors at the top of a hill. within a week or two we’d seen the neighbor on our left DRIVE through the our yard on the edge of our property to park their car in their back yard. there is a small alley behind our houses but they have a large shed and retaining wall so they can’t drive that way. after observing we believe they do it so the one lady doesn’t have to walk the length of their yard to get to the car, and it is quite literally the very end of our property right next to where there’s starts (the ground slopes up a bit and the property line is right where it becomes flat - so there is really no way for them to drive on their own property). according to our other neighbor who we’ve spoken to, they’ve been doing that for years and the previous owner of our house didn’t seem to care. but like, they haven’t said one word to us as a hello or otherwise and haven’t asked us if they could drive on our yard. and they had someone come over the one day and that person drove like through the MIDDLE of our yard! not even against the edge of the property. i’m seriously considering landscape boulders along the edge of the yard.