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Trailer skirts for improved fuel economy



As you drive along the interstates you’ve no doubt seen more and more trailers equipped with side skirts to improve aerodynamics and fuel efficiency. The relatively new devices are catching on quick. Highlighting the trend is a recent announcement by Interstate Distributors—that it’s in the midst of installing 2,000-plus side skirts, the cost partially offset by an EPA Diesel Emissions Reduction Act (DERA) grant.

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Sean Graham, president of Freight Wing, makers of the side skirts that Interstate selected, said the utilization of trailer  aerodynamics has reached a tipping point in the trucking industry.

“When we came out with side skirts six years ago, our primary challenge was to prove to fleets that they saved fuel,” said Graham. “So we invested heavily in SAE/TMC testing to quantify results, while working with fleets in their own testing programs. We’ve seen up to a 7% improvement in fuel economy when track testing at constant highway speeds. In real-world fleet operations, there are many variables that can impact performance. But, we’ve found that fleets typically report 4% to 6% improvements, depending upon their application and driving environment.”

With that, Graham said the ROI on side skirts is around 50,000 miles. So, it’s one of the lowest cost, biggest productivity performers out there. And fleets are beginning to realize they can save money and lower their carbon footprint at the same time.

It’s something not lost on the California Air Resources Board (CARB). This year, aerodynamic devices, such as side skirts and low rolling resistance tires, must be installed on new trailers. And by 2013, any trailer entering the state must have side skirts and fuel-efficient tires, unless fleets sign up for optional phase-in compliance plans.


Lee Owens, senior vice president of maintenance and facilities for Interstate Distributor Co., which is North America’s 12th largest truck load carrier and 46th largest for-hire carrier, said that even without the CARB mandate, his company would be moving toward trailer side skirts. “We always want to be on the leading edge with efficiencies and in the reduction of greenhouse gases,” he said. “We tested the side skirts for the past few years and have seen up to a 5% improvement in fuel economy depending upon the route and the speed we’re traveling. The higher the average speed, the better the performance. We also tested durability—a huge factor for us in deciding which side skirts to purchase. We chose the Freight Wing product because it was more resilient than others we tested.”

Freight Wing side skirts are constructed of durable plastic panels, combined with a flexible bracing system designed to absorb and deflect both ground and side impacts.

“And to Lee’s point, durability really is a key factor in any side skirt you purchase,” said Graham. “The fuel economy improvements from skirting have been well documented, but the second part of the equation is these things must hold up for fleets. After the designs were made to maximize fuel economy, we worked with different materials to make sure the side skirts had the flexibility to withstand and absorb impacts from the side and the ground in low clearance situations—like railroad crossings and steep loading docks. Flexibility is important, because the lower you get to the ground, the more fuel you can save.”


The fuel economy enhancements and long life of the side skirts is also why EPA bestowed an $875,972 DERA grant to the Pacific Northwest Pollution Prevention Resource Center (PPRC) to help Interstate offset the cost of the side skirts. Dan Brown, from EPA’s region 10, said that when awarding grants, they look for getting the biggest bang for their buck in the reduction of emissions while reducing fuel consumption. In this case, Interstate’s proposal, submitted in conjunction with the PPRC, fit the bill.

“There is a lot of competition for these grants—more requests than we have money—so we really look for results and community benefits,” said Brown. “With the PPRC and Interstate proposal, they’re looking at saving upwards of 1.1 million gallons of diesel a year, and over 16 million gallons over the lifespan of the skirts, while preventing 182,633 tons of greenhouse gas emissions. That’s a big impact to not only their company, but the environment, as well. Everyone wins.”

And, so ultimately, will all fleets as the adoption to side skirts continues.

The future of DERA Grants?
According to Dan Brown, from EPA’s region 10, another round of DERA grants is expected toward the end of the year. Fleets wanting to participate and qualify for funding must work with a non-profit agency in the submission of their proposal. Small fleets are not exempt from the program. They can work with the non-profit, which can then submit the proposal on their and other fleets’ behalf. Basically, if enough fleets in a


region want the same fuel saving/emission reducing device, the non-profit can roll the total number into one package, then submit the grant proposal. If the grant is accepted, the non-profit agency would then administer the program.

As for beyond 2011? At this point, Brown said it’s up to Congress to reauthorize DERA. “We know the program is extremely popular and it’s making an impact. We’re very hopeful it will continue in the years to come.” 

To learn more about upcoming DERA grants, click here.


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