[Big Dave]

I do agree that Class 8 trucks offer a lot of scope for fuel consumption reduction.

That said, the sheer flexibility of the “tractor-trailer arrangement” defeats any “silver bullet” anyone can come up with. There are trailers of every description and are used in a lot of different ways. Some lend themselves to improvements in FE, some are Mission: Impossible.

Take the most common trailer – the box van. Actually it has two versions. One is the purpose-built box van and the other is a type of flatbed that is specialized for standardized shipping containers. A trucker may simply drive to a destination, unhitch his trailer and pickup another (very common) or he may wait at the dock for his trailer to be unloaded and maybe reloaded for another run. Where the shipper owns the trailer (FedEx, Wal-Mart) and can control the usage of the trailer, you will see aero trailers. FedEx doubles in particular are rapidly going to aero features. But when you drop a trailer and grab another, the trailer owner has zero incentive fort any frills, because he doesn’t think he pays for the fuel.

On the other hand, a bulk trailer (dry stuff like flour or plastic pellets) might spend its entire service life hooked to the same tractor. But somewhere along the line somebody decided that the additional weight of fairing in a mobile adventure in piping imposed more of a weight penalty than the aero gain. The same is pretty much true of tank trucks. Old goats like me remember when truck trucks were nicely faired, but nobody has made a tank trailer like that since the 50s. Too expensive, too heavy, and the fairings tend to hide leaks.

Flats and auto delivery trailers (“rolling parking lots”) are probably beyond hope.

A subset of trucks that has a lot of scope for aero work is “expediters.” These are long-range (they have sleepers, road gearing and drive trains) straight trucks usually Class 5 or 6 but sometimes Class 7. These trucks generally haul light, time sensitive loads over medium distances – say Pittsburgh to Indianapolis. Time sensitivity means they have to run as fast as they can get away with and that opens the door for aero mods. The truck is all solidly attached so they tend to be owned by owner-operators and they are touchy about fuel.

Trucks severely need to get into CCTV rearview systems. Class 8 trucks are often festooned with three or four sets of side-view mirrors.