Side Skirts for Tractor Trailers
to Increase Fuel Efficiency

Whether they are called side skirts, air dams, air fairings, side fairings or truck fairings, we are referring to the devices that are installed under the sides of big truck trailers to reduce wind resistance (or air drag) and increase fuel efficiency.

Many professional drivers are familiar with fairings on the backs of their tractors to reduce wind resistance between the tractor and trailer or the low tractor fairings most often covering the fuel tanks. We previously wrote about aerodynamic wheel covers as a means of increasing fuel efficiency.

Here are what some websites have to say about trailer skirts:

  • "Advanced Trailer Skirts" were one of the "Verified Aerodynamic Technologies" listed on the EPA's SmartWay Technology page.
  • A PDF document from the EPA says that side skirts are "panels [that] hang down from the sides of a trailer at the bottom edge to enclose the open space between the rear wheels of the tractor and the rear wheels of the trailer."

  • An article on entitled "Aerodynamic Tractor-Trailers May Become the Rule in California" quoted SmartWay transport manager Mitch Greenberg as indicating that "side skirts improve fuel economy by 4%." (reference removed)

  • In March 2009, quoted Andrew Smith, CEO, ATDynamics as saying, "Trailer aerodynamic devices have gone from being fringe products to accepted, mainstream components all due to the dramatic fluctuations in fuel prices we've experienced lately." (reference removed)

  • An article stated the following about two new skirts "that accommodate larger wide-base tires" being revealed at the 2010 Mid-America Trucking Show in Louisville, Ky:

    "Produced by the Utility Trailer Manufacturing Co of Industry, Calif., both designs are verified through the Environmental Protection Agency (EPA) SmartWay program and the California Air Resources Board (CARB) as meeting governmental fuel efficiency standards."

    One of the products is said to provide a 4 percent savings in fuel, the other 5 percent.
    New-tractor-trailer-side-skirts-tailor-made-to-hem/ArticleStandard/Article/detail/662292 (reference removed)

  • Utility Trailer's website features a video and .pdf document with all of the details about their products.

  • At one time, Great Dane Trailers' website listed these "Aerodynamic Trailer Side Skirts" first among numerous products that are optional for their new or retrofitted trailers. (reference removed)

  • The Natural Resources Canada [NRC] website provides details on "How to select a trailer aerodynamic device." A photograph on their site reveals that the product they describe is slightly different from those most often seen in the USA.

    NRC says, "Trailer side skirts are a set of panels that run the length of the trailer to extend it closer to the ground." The devices "provide a 4 to 7 percent fuel savings by minimizing the air flow under the trailer and around the back axle." There is also a chart showing the average payback period.

  • A article quoted a truck owner who installed Windyne skirts on his trailer and "says they save 8.94 percent in fuel."

  • An April 22, 2008 article on states, "Creating an improved aerodynamic shape for truck trailers by mounting sideskirts can lead to a cut in fuel consumption and emissions of up to as much as 15%."

Vicki was delighted to find that numerous trucking companies have decided to implement these aerodynamic devices on their trailers. Let's take a look.

This rig is operated by Salson Coast to Coast.
Side skirt air fairing on semi tractor trailer.

Close-up of side skirt air fairing on semi tractor trailer. A close-up of the skirt reveals that this is a US EPA Certified SmartWay Trailer.

This is an ultra close-up of the seal that the side skirt bears.
Close-up of US EPA Certified SmartWay Trailer designation.

Aerodynamic trailer side skirt on a Landstar trailer. A Landstar trailer sports its aerodynamic trailer side skirt.

This Prime Inc trailer has one installed behind the fuel tank for the trailer's refrigeration unit. Prime trailer with side skirt air fairing.

This close-up shows the clearance behind the reefer's fuel tank. Close-up of side skirt air fairing on Prime trailer.

Difference in configuration of side skirt under a trailer. Whereas the skirt shown on the Prime trailer above has sloped sides, the one shown here has pointed sides. We're not sure, but it appears that the fairing may extend a little closer to the ground than the one above.

This J.B. Hunt trailer features a side skirt. J.B. Hunt trailer with a side skirt air fairing.

Artwork or advertisement on a Trans West trailer skirt. Up until taking this photo, the only writing we've seen on skirts is the EPA certification. This Trans West trailer's skirt is printed.

Close-up of Trans West side skirt showing printing. Here's a close-up of the Trans West side skirt. We wouldn't be surprised if some day in the future, this turned into advertising space.

Please notice that some trailer skirts (whether shown on this page or on linked pages) have different configurations. We noted the skirts' edges above. Of particular note to us is the straight (in line with the sides of the trailer) versus sloped (narrower toward the front of the trailer and fanning out toward the sides of the trailer toward the rear) installation. We would be interested in knowing which configuration works best to reduce the most wind resistance.

We would also be interested to read drivers' experience in using different brands of trailer skirts. Which skirt resists cracks and breaks, holds up under temperature and humidity changes, lasts longest and in general works the best?

truck drivers money saving tip icon

Money saving tip: Any device used on a vehicle to reduce wind resistance or air drag will help improve that vehicle's fuel efficiency. There is absolutely no doubt that tractor trailer side skirts or air fairings accomplish both.

Professional drivers who own their own trailers would do well to calculate the ROI (return on investment) that purchasing and installing these devices will provide. While costs may vary between brands, one driver stated:

"With the cost of the Windyne Flex-Fairings being $4,600 U.S. ($5,000 Canadian), it will take approximately 13.6 months to pay for the fairings. With an expected life cycle of 10 years, my total dollar savings (at today's fuel prices) will be approximately $39,000."

Overdrive Online uses the "default prices of around ... $1,800 for side skirts" for which they say "the EPA estimates a payback of about a fuel savings alone."

Notice, too, that the payback period range (shown graphically on the NRC website) shows two different types of skirts: standard and advanced. The EPA's website provides a list of SmartWay verified technologies and devices, including those classified as one of these two types of skirts.

In some places, incentives such as grants may be available to help drivers purchase trailer skirts. If you are interested, investigate all opportunities and take advantage of the one that works best for you.

Be aware that some locations may require drivers to have these devices installed on their trucks before they can enter. Know ahead of time what restrictions are involved before you make the trip.

When you calculate your ROI, be aware that your driving habits also affect your fuel savings.

Furthermore, determine if the quoted cost of the skirts includes installation.

Return from Side Skirts for Tractor Trailers to Increase Fuel Efficiency to our Truck Operations page or our Truck Drivers Money Saving Tips home page.

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