After several years of testing showed trailer side skirts save considerable fuel and therefore cut exhaust emissions from tractors that pull them, Interstate Distributor Co. has begun installing them on 2,058 reefers and dry vans at its maintenance facilities in the Pacific Northwest.
Interstate Distributor Co. will install Freight Wing AeroFlex skirts on 2,058 reefer and dry van trailers as part of a grant program. More trailers will follow, the fleet says.
Interstate Distributor Co. will install Freight Wing AeroFlex skirts on 2,058 reefer and dry van trailers as part of a grant program. More trailers will follow, the fleet says.

Paying part of the undisclosed cost of Freight Wing Aeroflex skirts is an $875,972 grant from the Environmental Protection Agency's Diesel Emissions Reduction Act (DERA), which will reduce payback time to about 18 months compared to nearly 24 months without the government money, said Lee Owens, senior vice president of maintenance and facilities.

"We've tested the side skirts for the past few years and have seen a 3 to 5 percent improvement in fuel economy depending upon the route and the speed we're traveling," Owens said. "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."

AeroFlex skirts consist of durable plastic panels combined with a flexible bracing system designed to absorb and deflect both ground and side impacts, said Sean Graham, president of Freight Wing. They save fuel by preventing wind from hitting the trailer's wheels and axles, thus reducing aerodynamic drag.

Interstate applied for the grant through the non-profit Pacific Northwest Pollution Prevention Resource Center. PPRC said the Interstate project is expected to save 1.1 million gallons of diesel a year, over 16 million gallons over the 10 to 15-year lifespan of the skirts and trailers, while preventing 182,633 tons of greenhouse gas emissions.

This is part of EPA's strategy to help truck operators cut fuel use and therefore reduce greenhouse gases, said Dan Brown of EPA's Region 10 in Seattle. Fleets can apply for grants through non-profit groups like PPRC, and through local, regional and tribal governments who participate in the program.

The Freightway skirts are EPA SmartWay certified, so they meet the aerodynamic requirements of the California Air Resources Board's recently implemented rules and allow the trailers to travel inside California.

But "I believe we would have leaned that way whether there was a mandate or not, due to what we've tested," Owens said. And Interstate has used aerodynamic tractors, auxiliary power units, low-rolling-resistance tires and other devices to save fuel, and has been an EPA SmartWay member since 2004.

Interstate will continue to outfit its remaining long-haul trailers with side skirts after this PPRC project is completed, Owens said. "The benefits are too big to ignore," he said. "We see the future for aerodynamic technologies as a key ingredient for reduction of green house gases and reduction of carbon footprint. Our plan is to be 100 percent compliant with the CARB mandate as it is presented now."

The fleet has engine shut-down parameters set for after five minutes of idle when a truck is equipped with an APU or shore/battery power that takes over heating/cooling duties from the main engine. "On our APU-equipped units we average 5.09 percent engine idle time," said Owens. "That's phenomenal."

The company is also committed to driver education. "We have peer groups and we closely monitor driver performance through telematics and engine data tracking. In prior years, the gap between our best driver and worst driver in fuel economy would exceed 1 mpg. But since we began monitoring, and mentoring through our peer group, that gap has closed significantly. If you implement fuel-saving technology, correct equipment specifications and couple that with solid driver training, you will maximize fuel economy."

Owens continued, "Over the past five years we've seen overall fuel economy improve by more than 1 mile per gallon to the high 6's. We run aerodynamic models from Freightliner, Volvo and Kenworth equipped with power and drive train components to maximize fuel efficiency."

Headquartered in Tacoma, Wash., Interstate Distributor Co. ( provides varied nationwide transportation services with more than 2,000 tractors and 6,800 trailers. It was founded in 1933 and now has more than 2,700 employees.

Seattle-based Freight Wing ( manufactures and distributes trailer side skirts, belly fairings, and gap fairings and customized products for a variety of trucking applications.

Pacific Northwest Pollution Prevention Resource Center ( is a regional non-profit that offers practical technical assistance to businesses, public agencies, and other non-profits that seek to conserve resources and save money.