A few weeks ago on the interstate I was behind a Fed Ex van whose back door was swinging open and closed every few seconds. There were packages on the floor within a foot or two of the open door sliding around.
I pulled up beside him and tooted (not blasted) my horn and then gestured multiple times at the back of his van. His response was to flip me the bird and speed off.
I feel sorry for the people whose boxes probably ended up on the highway.