[Big Dave]

With double or triple trailers, you don’t reverse. These truck trains operate strictly terminal-to-terminal they are then taken to their destination as singles.

The advantage of doubles or triples is that you can spread the load out to more axles. Most trucks “cube out” – that is they fill the trailer volume with a load weight less than maximum. so doubles and triples often are not as heavy as they look.

At the other extreme, ever seen the “Michigan centipedes?” Michigan limits the weight of load per axle but not overall. So you see single trailers carrying heavy loads with 40 wheels under them.

Actually a pioneer in aero trailers is Wally World. The reason trailers have not received much aero treatment is that truckers usually drop off a box trailer and pickup another, so he has no investment in it. With Wally World, they own all the trailers and the trucking operations so they have really good reasons to dictate aerodynamic trailers and have the wherewithal to make that work.