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The role of aerodynamic devices to boost fuel efficiency and reduce emissions has been tapped, but not exhausted, for tractors and trailers, the North American Council for Freight Efficiency found in recently released updates of two confidence reports first issued in 2016.
“Fleets can see significant fuel efficiency improvements when they invest in aerodynamic devices for their tractors and trailers. There are a host of devices to choose from and we lay out the benefits and challenges of each type of aero device,” NACFE Executive Director Mike Roeth wrote in an email.
NACFE noted modern tractors at highway speeds are capable of exceeding 10 mpg fully loaded compared with their non-aerodynamic predecessors that were “lucky” to get 6 mpg.
The confidence reports — Tractor Aerodynamics and Trailer Aerodynamics — seek to give the industry a foundational understanding of tractor and trailer aerodynamic devices, provide an unbiased review of available aerodynamic technologies on the market today, and increase the investment into cost-saving aerodynamic technologies.
At the same time, NACFE pointed out the need for both vehicle manufacturers and manufacturers of add-on aero devices to make sure devices will work on alternative-fueled vehicles.
The most significant development in tractor aerodynamics has been a focus on drive wheel fairings, tractor-trailer gap devices and the replacement of mirrors with cameras. With trailer aerodynamics it has been the sunsetting of first-generation trailer tail devices and the rise of a new generation of rear devices that address some of the concerns with first-generation devices, including driver acceptance and docking, according to NACFE.
It noted tractor aerodynamic technologies and strategies are constantly and rapidly evolving. In the updated report on tractors, NACFE focused on three areas: the cab, the frame/chassis and part removal or relocation.
While OEMs view the entire tractor as a unified system interacting with the air flows, additional aerodynamic devices can be added to tractors. These include cab extenders, roof extenders, tractor-trailer gap devices, mirrors and cameras, sunshades, headlamps, bumpers, chassis fairings, drive-wheel fairings, fifth-wheel location and height, wheel covers and vented mud flaps.
NACFE also emphasized truck OEMs “should design and make available aerodynamic features for day cab tractors, as the industry migration to shorter hauls will likely result in more day cabs seeing significant highway and interstate miles.”
In the confidence report on trailers, NAFCE stated “fleets will see the greatest benefit from adopting multiple aerodynamic devices. However, the net benefits from the package of devices will not simply equal the sum of the benefit of each individual device, making it difficult for fleets to prioritize investment decisions and feel confident on their paybacks.”
Reducing the aerodynamic drag of a basic van trailer, the most common trailer, comes down to adding one or more devices onto three key areas of the trailer: the gap, the underbody and the rear. The report detailed the devices for improving the aerodynamics in these three key areas, as well as “more novel” options, such as vortex generators, wheel covers and mud flaps.
NACFE pointed out the Environmental Protection Agency and National Highway Traffic Safety Administration’s GHG Phase II rules initially required the use of aerodynamic devices for new van and refrigerated trailers longer than 50 feet in 2021, with voluntary compliance starting in 2018. Final implementation of the trailer rules has been delayed pending legal and regulatory reviews.
In coming years, regulation is likely to continue to drive adoption of trailer aerodynamic devices, NACFE forecast.
In both updated reports NACFE used a matrix to plot the various technologies in terms of the expected payback in years compared with the confidence NACFE has in the available data on that technology.
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