Trailer aerodynamics comprise the least accepted type of fuel-saving methods, according to a study by the North American Council for Freight Efficiency. It appears that it took a government decree to push operators into it, and it will take another set of rules to force further adoption of drag-reduction methods for trailers.

Those are among the takeaways from the NACFE’s 2016 Annual Fleet Fuel Study. Participating were 17 large American and Canadian fleets, admittedly representing only 4% of the long-haul tractor-trailers on the road. And the adoption figures reflect companies, not the numbers of vehicles they have, NACFE said.

Some of the fleets are well-known and most have the resources to analyze results from various technologies to determine if they’re worth spending money on.

The study included 69 fuel-saving technologies that were grouped into seven categories: tractor aerodynamics, trailer aerodynamics, powertrains, tires/wheels, idle reduction, chassis, and fleet practices. Of those, trailer aerodynamics had the lowest acceptance rate, about 21% of the fleets surveyed.

Much more popular, with almost a 65% adoption rate, were tractor aerodynamics and low-rolling-resistance tires, the study showed. You know this is true if your memory extends beyond the turn of the 21st century, maybe even back to the first Arab Oil Embargo of 1973. Roof-mounted air fairings began appearing on tractors in the mid-‘70s as fleet managers reacted to spiking oil and fuel prices. Tractors led every big rig into the speed-induced wind, so were obvious targets for improvement. (Easy-rolling tires came much later.)

A few thinking managers began using aero devices on trailers not long afterward. By the late ‘70s I was living in California and went through the second oil embargo of ’79. I recall seeing Nose Cones on a few trailers and truck bodies. Aside from fuel savings, one argument for them was steadier, safer handling of the trailer and therefore the entire rig.

In 1980, Peterbilt released results of an experiment with an aerodynamic trailer that said its deep skirts and “truncated” (but non-folding) boat tail gained 1.5 mpg for the tractor pulling it. Fruehauf’s FEV2000 tractor-trailer got 7.4 mpg in tests – 72% better than a non-aero rig, the company claimed. But fuel at that time was still too cheap, and the concept of streamlined trailers too radical, for truck operators to care.   

It took more than 20 years for other devices, including now widely used trailer skirts from various makers, to appear. By then fuel prices had gone up much more, and skirts began paying off. But they saved nothing when trailers were parked in terminals and customers’ lots, and for some operators that could be two-thirds or more of their trailer fleets.

The NACFE study shows that the 17 participating fleets didn’t begin to adopt trailer aerodynamics until 2008, just about the time that a state law in California required the adoption of fuel-saving devices on trucks. That’s also when the Air Resources Board announced that it would write rules to enforce the law. CARB’s rules phased in beginning in January 2010 and the rest, as the cliché goes, is history.

The rules affected box-type trailers 53 feet long or longer. Most fleet executives were less than enthusiastic, saying the skirts and other devices required to meet CARB rules cost more to buy, install and maintain than they saved in fuel.

I recall one exec remarking that he and his colleagues had considered buying 50-foot trailers to get under the CARB requirements. But they figured CARB would then change the rules to include them, too. (His fleet is one of the 17 in NACFE’s 2016 study, by the way.)

Execs at another large fleet in the study tried to designate trailers by “California” and “non-California,” and equip only those that went there. But an analysis showed that a big majority of the carrier's trailers sooner or later went to the Golden State, so it began installing the equipment on all of them. Eventually, component prices came down and payback periods became shorter, even though lower fuel prices tend to stretch the return on investment time.  

While the 21% adoption rate for trailer aerodynamics is still relatively low, it will no doubt increase because trailers are a major focus of the federal Phase 2 Greenhouse Gas rules released last month. Expect more skirts, boat tails, nose fairings and other devices to appear as time goes on. Even the basic shapes of trailers might change – like it or not.