Green Transport Partnership
                A  Glance  at Clean  Freight  Strategies:
                Improved  Aerodynamics
Better
aerodynamics
reduces fuel
consumption
and emissions
that are
harmful to the
environment.
 An aerodynamic truck tractor with
 integrated cabroof fairing
What is the  challenge?

Aerodynamic drag (wind resistance) dominates truck
energy losses at highway speeds. All vehicles derive a
benefit from reducing aerodynamic drag. The
longer the drive and the higher the speed, the
greater the benefit. Manufacturers have focused
considerable attention on improving truck tractor
aerodynamics over the past two decades, and the
drag coefficient (a measure of a vehicle's wind
resistance) has fallen from about 0.8 in 1970 to
about 0.65 for a typical truck today. Aggressive programs to reduce drag could result
in further 20-percent reduction in the drag coefficient. According to the Department of
Energy, a 10-percent reduction in aerodynamic drag results in a 5.5 percent fuel
savings at highway speeds.
                          What is the

                          solution?
                          A number of options exist for improving
                          aerodynamics and achieving significant gains
                          in fuel efficiency.

                          Tractor Aerodynamics
                          Numerous aerodynamic devices are available for truck tractors, including roof fairings
                          (an integrated air deflector mounted on the top of the cab), cab extenders (sometimes
                          called gap seals, which help to close the gap between the tractor and the trailer), side
                          fairings, and a front bumper air dam (which reduces air flow underneath the truck). All
                          major truck manufacturers now offer aerodynamic models that include a sloped hood,
                          streamlined front profile, and a full package of add-on devices. These models can
                          improve fuel economy by over 15 percent, particularly when compared to a "classic"
                          profile tractor.
Air deflectors on single-unit trucks
               Office of Transportation and Air Quality • Mailcode? •  October 2002 • EPA 420-F-02-031

-------

Trailer Aerodynamics
Several options exist for improving trailer aerodynamics. According to the American
Trucking Associations (ATA):

  • Reducing the tractor-trailer gap from 45 to 25 inches will help limit the drag
    caused by air turbulence and improve fuel economy one to two percent.

  • Rounded air deflector bubbles (pictured) can be installed on the front side of van
    trailers to cut wind resistance and improve fuel economy up to five percent.

  • Trailer side skirts-panels that hang down from the bottom of a trailer to enclose
    the open space between the rear wheels of the tractor and the rear wheels of the
    trailer-are another innovative option.

  • On flatbed trailers, drag can be  reduced by arranging cargo to keep the outline of
    the total load as low and smooth as possible.

  • Researchers in Europe have shown that securing loose tarpaulins will improve
    fuel economy by up to 2.5 percent.

  • Closing the curtains on an empty curtain-sided trailer improves fuel economy by
    4.5 percent.

Single  Unit Truck  Aerodynamics
Many new single-unit truck models incorporate a sloped  hood and more streamlined
front profile as a standard feature in an effort to reduce drag. Rounded air deflector
bubbles can also be added to single-unit trucks with van-style  bodies to reduce fuel
consumption by five to ten percent.
  The  results are in.,
Using a streamlined profile tractor with aerodynamic devices (roof fairing, cab extenders,
and side fairings) will reduce fuel costs by $900 and eliminate over six metric tonnes of
carbon dioxide emissions per year compared to a classic profile tractor. When installed
on van trailers, aerodynamic devices can produce similar fuel and emission reductions.
Some aerodynamic options now come standard on many trucks, like a streamlined
hood. Others must be purchased and installed for an additional cost. The initial expense
of these options are often quickly recouped through fuel savings.
Next steps
Trucking firms should buy optional aerodynamic equipment when purchasing a new
truck. Many firms also sell devices that can be added to existing trucks. The fuel cost
savings more than outweighs the additional costs of these devices and reduces
harmful emissions that can damage the environment. For more information on
aerodynamic devices, contact your truck dealer or the ATA. ATA's Technology and
Maintenance Council has released publications that quantify the fuel economy
benefits of a variety of aerodynamic options.
   Printed on Recycled Paper

-------