bi-wing trailer vanes coming to 18-wheelers ?
 

AeroStealth and his wife came by for a brief visit before returning home this morning, after a trip to celebrate a daughter's wedding in Missouri.
At dinner last night he showed me some photos of an 18-wheeler he spied crossing New Mexico, sporting a bi-wing, trailer vane setup, presumably for drag reduction.
We may hear about this one day. I give it an initial thumbs down. While it may make a difference on an aircraft, in 2-D flow, no device of this type ever made a difference in an automotive application of 3-D flow.