ATDynamics, Inc. has launched the TrailerTail, an aerodynamic device claimed “...to increase fuel efficiency of long-haul tractor-trailers by greater than 5%” at highway speeds. It’s an extension mounted to the rear of a standard van trailer, and “in less than 8 seconds collapses from 4 ft to a few inches in length” to enable normal trailer door operation.

This patented drag-reduction device’s fuel-saving potential has been documented in SAE J1321 third-party tests, the maker says, and the devices are components on EPA SmartWay-certified trailers. Wind tunnel and on-road tests conducted in partnership with major fleet vehicle operators have shown the TrailerTail's ability to reduce tractor-trailer drag by 12-20%, the company says, by creating a smooth airflow at the rear.

They’re currently available as retrofits to any existing swing-door trailer application or as factory-installed options on some OEM trailers.

But there’s a catch: the device adds 4 ft to the overall length of a trailer, which makes it illegal in every Canadian province. In the U.S. there’s an exemption of 5 ft for aerodynamic extensions. The manufacturer is working to resolve the Canadian issue, and at least one fleet here – Quebec’s Transport Groupe Robert -- is apparently interested in pursuing it.

TrailerTails don’t inhibit the use of a trailer's rear doors and require minimal effort for opening and closing. Drivers are said to think that the devices make driving easier by providing additional stability and reduced spray at the trailer’s rear. The device collapses when a driver opens the rear doors. Patented hinge systems allow swing-door trailers to access loading bays normally. Roll-door variations will be available commercially in 2009.