The driver had too much money that he didn't know what to do with, needed some more wind resistance to reduce his fuel mileage, and wanted to add some unproductive weight to his rig to reduce it's hauling capacity! Ah, vanity.
many years back was a guy around here had a long nose 9500 with an old mercury bunk and dual straight pipes...but also had a pantyhose burner coming out the right side..stacks were for show only..different strokes for different folks?!
Actually PACCAR does that quite a bit now, but all the ones I have seen had dummy stacks on the sides of the cab as usual and the real exhaust exited under the truck. They do this because the new trucks exhaust gets so hot when it regen's that it will blue and melt a regular chrome stack. If you notice on trucks with a DPF system, they have what they called "inter cooled" stacks, in which where the tip has an inner and outter side to it. They do this to keep the shiny chrome from peeling off. No idea why this guy ran 3 stacks, cuz the whole point is to keep it clean appearance Many custom truck builders run those 8" and 9" stacks on the sides of trucks and place the working exhaust out the bottom by the rear axle, so they don't ruin and carbon the big expensive pipes.