The efficiency of converting energy in motion — no matter the source of that energy — always depends on the aerodynamic design of the object in motion.
Truck makers have made huge strides in improving the aerodynamics of the base models of many of their trucks. In addition, there are a host of add-on devices that can improve tractor aerodynamic efficiency even further.
But even the most aero tractor is only as efficient as the trailer attached to it. Thankfully, there are many products fleets can select that deal with the three most common areas that negatively impact the aerodynamic efficiency of a trailer: the tractor-trailer gap, under the body of the trailer and at the rear of the trailer.
When it comes right down to it, aerodynamics is a numbers game. Moving from 6 mpg to 10 mpg for one diesel truck leads to 6,667 fewer gallons of fuel burned over a 100,000-mile year, a 40% reduction in costs and emissions. That translates to more than 666,000 gallons of fuel not burned in a year for a fleet of 100 trucks. At $3/gal, that one fleet is saving $2 million. For the 1.7 million tractors on the road today, that equates to a savings of $34 billion, as well as significant reductions in both carbon and particulate emissions from not burning the fuel in the first place. While aerodynamic improvement does not account for all of that savings, it plays a significant part in a fleet’s overall efficiency.
In 2016, North American Council for Freight Efficiency (NACFE) first tackled the subjects of tractor and trailer aerodynamics when it published Confidence Reports on each of those subjects. Earlier this month, we released updates to those initial Confidence Reports on tractor and trailer aerodynamics. We did so because some things have changed that could impact a fleet’s decision to invest in this technologies.
The most significant developments in tractor aero are an increased focus on drive wheel fairings, tractor-trailer gap devices and replacing mirrors with cameras. With trailers we saw the disappearance of what we are calling the first generation trailer tail devices — devices that we thought showed a lot of promise when we issued our initial trailer aerodynamic device report. For a variety of reasons — not the least of which were the need for driver engagement to deploy them, maintenance issues and issues with docking trailers outfitted with these devices — these devices failed to gain widespread acceptance. Fortunately, we have some very creative, innovative people in the trucking industry and they developed a new generation of trailer tail devices that address the concerns the market expressed with the initial iteration of trailer tail devices.
I suspect we are not done seeing ways to improve aerodynamics on today’s vehicles — and if needed we’ll update these Confidence Reports again.
One final thought, I hope that as manufacturers of alternative powered vehicles are working on their prototypes and pre-production models that they will not only make base models aerodynamic but also make sure their design engineers allow for easy installation of add-on aero devices. After all, freight efficiency matters regardless of the fuel source powering the vehicle.
Michael Roeth has worked in the commercial vehicle industry for nearly 30 years, most recently as executive director of the North American Council for Freight Efficiency. He currently serves on the second National Academy of Sciences Committee on Technologies and Approaches for Reducing the Fuel Consumption of Medium and Heavy-Duty Vehicles and has held various positions in engineering, quality, sales and plant management with Navistar and Behr/Cummins.
