Safety while stopping overnight to get some sleep

If I'm trying to make as many miles as I can in a day, I don't hesitate to stay in a "proper" rest area (not one of those tree-screened, unlit, no facilities wide spots in the road), usually where the trucks are, or at truck stops right off the highway. Never had a problem. When I'm inclined to mosey, I do like a campground, but that takes planning and a bit more time.