How to Improve Fuel Efficiency with Trailer Aerodynamics

There are many things you can do today to help improve your fleet’s fuel economy. In addition to following practices like ensuring your tires are properly inflated and maintaining a steady speed, you can also add aerodynamic devices to your trailer that will help to reduce drag and improve overall fuel efficiency.

Maximum aerodynamic improvement comes from using a combination of aerodynamic devices to help reduce effective drag area and streamline airflow. Some of these devices include:

Trailer Skirts

Trailer skirts hang from the sides of the trailer, from the landing gear to the rear wheels, to help reduce the drag area by guiding air around the sides and back of the trailer. According to NACFE, trailer skirts are the most popular devices for addressing drag, offering 1 percent to more than 5 percent fuel savings versus non-skirted trailers.

Rear Fairings

Rear fairings can help to reduce drag from the low-pressure developed in the wake behind the trailer. Trailer – or boat – tails typically consist of collapsible panels that fold out from the rear of the trailer. While these are effective at reducing drag, they can be complicated to use and make it difficult for drivers to gain access to the rear doors of the trailer. Another option is rear fairings that are constructed with panels located on the sides and top flush with the edge of the trailer. This type of design helps to bend airflow around the back of the trailer to reduce drag without affecting the ability to open and close the rear doors. Testing performed by the American Trucking Association (ATA) on a variety of rear fairings showed that most provide between 5 and 15 percent fuel efficiency.

Nose Fairings

Arguably the worst area of low-pressure on a tractor-trailer is the section between the back of the tractor and the front of the trailer. It has also proven to be one of the most difficult areas to address aerodynamically. Devices like trailer nose fairings or nose cones, however, can help to close the gap between the tractor and trailer, reducing airflow and streamlining the airflow from the tractor to the trailer. A NACFE study found that these types of gap reducing devices can provide 1-2 percent fuel savings.

Aerodynamic Mud Flaps

Mud flaps are used to help protect vehicles and pedestrians from mud and flying debris. However, the typical design of a mud flap – a solid rectangular sheet – catches the wind under the trailer and can create additional drag. Vented mud flaps can be used instead to help resolve this issue. The vented design still helps to reduce spray, but is more aerodynamic and allows air to flow through the flaps, which reduces movement when the trailers are running at high speeds. One study performed by Exa Corporation found that vented mud flaps can provide an estimated 2.7 percent fuel savings based on the drag reduction.

Which Device is the Best? 

There’s no one-size-fits-all answer to this question. While each of these devices can provide fuel efficiency benefits alone, fleets will see the best results when two or more devices are working in tandem. According to NACFE, all fleets should be considering adding aerodynamic devices to their trailers as the potential fuel savings are likely quite high– up to 10 percent – for the majority of fleets. Also, many regulations are likely to require the use of aerodynamic devices in the coming years, so fleets should consider integrating these devices in anticipation of upcoming mandates.

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