aero transport !!!
 

Boat Tail Reduces Truck Fuel Consumption By 7.5 PercentScienceDaily (Nov. 5, 2009) — A boat tail, a tapering protrusion mounted on the rear of a truck, leads to fuel savings of 7.5 percent. This is due to dramatically-improved aerodynamics, as shown by road tests conducted by the Dutch PART (Platform for Aerodynamic Road

We may well be seeing these semi trailers being manufactured with the boat tail built into the rear. Perhaps a hydraulic boat tail that can expand and contract as needed to accommodate the loading dock and various loads.
A fleet of boat tailed trailers would provide a distinct advantage to the Company using them. 7% of a semi's yearly fuel bill is large.

I have seen several of this type of tail already in use. The other day I even saw a fully tricked out rig with side skirts, boat tail, and smooth wheel covers! the tails I have seen a about half the length though so probably not 7.5% gain

Yup, the first time I saw one, I mashed the gas to check it out. Ecofail. :-p