We rarely see carpets this difficult in homes but these can be fairly commonplace among rentals. Here are two carpets on different properties that demonstrate what a little low moisture muscle can produce. Both carpets suffered from similar types of high traffic wear that was the result of walking off of the parking lot directly onto the carpet. In both instances there was nothing else to wipe off the tar and grime.
NOTE: if the screen pictures don't automatically slide, hit the arrow head on either side of picture.