A rear end taper measuring slightly more than 400 mm in length forms a crucial part of the aerodynamic concept. It features folding elements to facilitate access to the load compartment. The rear end taper improves wind resistance by a further 7%.

Crowdsourcing a different approach to optimizing trailers
Brad Bennett, a designer in British Columbia, is proposing a retractable trailer unit as a different approach to reducing wind resistance and fuel consumption when deadheading (returning empty).
Bennett said that his research found that semis tend to travel from 15% to 50% empty over the distance of their trips—especially short haul rigs that range around 200 miles from base.
Bennett’s plans call for the trailer walls to be made from strong composite materials so the walls will be narrower allowing the interior space to remain almost the same. The back door will roll up and the walls will ride on a electric gear track assembly. Loading-wise, it’s still basically the same trailer, Bennett says.
Photoshopped rendering of retractable trailer concept. Click to enlarge.
Bennett is welcoming comments on his concept.

Mercedes-Benz says that the 18% reduction would result in a reduction in fuel consumption amounting to almost 5% in real-life road traffic. In the case of an average mileage of 150,000 km a year this means a saving of some 2,000 liters (528 gallons US) of diesel fuel and a reduction of more than five tonnes of CO₂.

The dimensions of the load compartment remain unaffected by the design. The familiar box—13.6 m in length, 2.55 m in width and with an overall height of 4 m—remains available for the freight, just as before. The aero trailer’s only restriction is the fact that its length measurement exceeds the currently permissible limit by almost half a meter, due to the tail-end extension. The handling and maneuverability are not compromised by the taper, according to Mercedes-Benz. This does highlight the need for changes to legislation, as in the case of tail lifts and transportable fork-lift trucks, for instance, where exceptions of a similar magnitude are already granted, the company suggested.

The aero trailer is the flagship of the new “Truck and Trailer 7plus” initiative being launched by Mercedes-Benz. By taking a holistic approach to the tractor unit and trailer it aims to considerably cut the fuel consumption even further than is currently the case. The basis of the “Truck and Trailer 7plus” formula is the fuel consumption of the new Mercedes-Benz Actros, which more than 7% lower than its predecessor model.

Tests in the wind tunnel and on the road prove that considerable further consumption progress is possible for semitrailer tractors. As an example, measurements taken in the wind tunnel at Mercedes-Benz have shown that a side trim panel on the trailer cuts wind resistance by 8%.

During test drives on the Record Run route this translated into a real-life consumption benefit of some 2% for a semitrailer tractor weighing 40 tonnes. In the case of an average annual mileage of 150,000 km in long-distance transport this results in a saving of around 750 liters of fuel.

In addition to this, at the instigation of Mercedes-Benz, a working group of truck and trailer manufacturers under the umbrella of the German Association of the Automotive Industry has carried out further tests on the aerodynamics of semitrailer tractors. In the framework of this study, measurements in the wind tunnel at Mercedes-Benz concluded that modifications to the cab such as a supposedly aerodynamic extension result in merely minimal improvements where wind resistance is concerned.

There is much more potential in aerodynamic measures at the tail end of the trailer; a minor extension of the tail end in the form of a “boat tail” brings significant benefits. Four flaps measuring just 400 mm in length and positioned at an angle reduce the wind resistance of the entire semitrailer tractor by nearly 10%. In arithmetical terms this corresponds to virtually 3% less fuel consumption or more than 1,000 liters of diesel a year. This is also shown by the simulations which have been carried out for the aero trailer.

As part of its “Truck and Trailer 7plus” initiative Mercedes-Benz is working on further holistic measures aimed at lowering fuel consumption. One of the projects involves the inclusion of information on the trailer’s tires in the tire pressure display in the cab of the new Actros.

The FleetBoard subsidiary is also currently developing methods of integrating the trailer in its systems. This forms the basis for concrete opportunities for increasing economy and therefore environmental compatibility to an even greater extent—for example, selecting the nearest available suitable trailer for a particular job, correctly allocating truck and trailer, and transmitting trailer data to the truck’s cockpit.