Most people who have spent much time in and out of the south know that
good old fat southern boys throw litter in the back of their pickups to
be blown out onto the already horribly littered southern roadsides.
What may not be as well known is that there are residual accumulations
of litter in the backs of those pickups.  Empty McDonalds sacks,
Walmart sacks, empty paper cups, unwanted styrofoam, etc. blow out
pretty easily with enough speed and wind.  Heavier items though, such
as pieces of rubber hose, metal objects, small tires, old shoes, trash
from construction sites, etc. do not blow out very easily.
Accordingly, such litter remains in the truck and accumulates.  If one
is walking through a parking lot in the south, it is interesting to
look in the backs of the pickups and observe the southern pickup litter
residue.