Triple Trailer FedEx truck

Dance of the Triple Trailers

You know you are not in Connecticut anymore, or Arkansas, or just about any other place in the Eastern U.S., when you begin to see trucks on the Interstates with three trailers in tow. Triple trailers or triples, also disparagingly labeled wiggle boxes or swing tails, are most often found on the Interstates in the less populated areas of the West (California being a notable exception), where the drivers of other vehicles are wise to give them all the highway they want.

“If a triple changes lanes too sharply, or gets hit by a crosswind, the rear trailer can start to do a little dance,” said a triple trailer FedEx driver I talked with at a truck stop off I-90 near Bozeman, Montana.

On that trip I’d first noticed triple trailers in Southern Utah, as I headed north on I-15 between Las Vegas and Salt Lake City. Many were operated by Saia, a freight line that specializes in LTL, or less than truckload, shipments. But the majority displayed the markings of either UPS or FedEx. And I was curious to know why.

“Mostly, it has to do with weight, and making the sorting of small shipments easier,” the FedEx driver near Bozeman told me as we walked around his rig while he checked tires and lines and connections.

If I have this right, Interstate highways, which for the most part are the only roads triple trailers are allowed to operate on, have a combined weight limit, which without special permits is 80,000 pounds. If a truck is carrying a heavy load, such as bags of fertilizer or cases of Dinty Moore Beef Stew, it might reach its maximum weight before even one trailer is full, which can be inefficient, and cost-consuming. However, because the kind of shipments UPS and FedEx specialize in are lighter for their volume than most other cargo, they can fill the three trailers without going over the maximum weight. Among other things, that means they can deliver the same amount of parcels with fewer drivers.

Also, when FedEx and UPS triple trailers are at a regional sorting facility they can be loaded and unloaded and their cargo sent off in different directions with more speed and efficiency than if everything was in a single trailer.

Before we got back in our vehicles and headed west on I-90 again, me planning to get in another 300 miles by the end of my day, he another 600 by the end of his, I asked if there were any safety tips involving triple trailers he’d like to share with motorists.

“The main thing is to keep off my tail,” he said. “Because when that rear trailer starts dancing, you don’t want to be its partner.”




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