https://ecomodder.com/forum/showthre...ero-38795.htmlBetween whatever drag and increased weight-related rolling-resistance penalty the flatbed incurred, it didn't seem to impact the mpg dramatically.
The trailer would have aggravated frontal area on both sides some. The width and porosity may have increased turbulence and prolonged turbulence, as it really wouldn't have any facility for 'calming' the disturbance.
If your version of Hucho's chapter on commercial vehicles still shows a bus in 'convoy' driving, at varying following distance, you'll see how low the Cd is for the trailing bus at close proximity, and how it lowers the Cd of the tow bus in a 'NASCAR' two-'car' draft.
A light-bodied, 'wake-rider' trailer, half the length of the bus, with some modicum of aft cross-section contraction, would seem unlikely not to get you near a null effect, even with the weight penalty.
I'll try to link to the Greyhound Bus and trailer concept:
It's at #4 (permalink )