If you noticed, the article talked about aerodynamics in terms of frontal area and side fairings - on other words, the parts of the tractor interacting with the

If you noticed, the article talked about aerodynamics in terms of frontal area and side fairings - on other words, the parts of the tractor interacting with the airstream. The trailer's leading edge is, well, a large, flat, un-aerodynamic rectangle. Lots of potential for aero improvements there. I sometimes see boat-tails etc attached to trailers, but my understanding is that they are usually attached (an unattached at destination) by tractor owner, as trailer owner doesn't pay for fuel costs. Could be wrong on that though.