The huge IAA commercial truck show in Hanover, Germany, late last month included this eye magnet, the "aerodynamically optimized road train" from MAN and Krone, both prominent vehicle builders in Europe.

The concept rig could save 25% in fuel and carbon dioxide emissions over current cargo carriers now used in Europe, MAN said in a press release. But it would require liberalization of the European Union's strict length regulations, as would another aero exercise from Mercedes-Benz and Schmitz Cargobull that was parked a couple of blocks away.

Unlike the Mercedes-Schmitz rig that could physically go to work tomorrow, the MAN-Krone road train is strictly a rolling concept with no powertrain in its Concept S tractor and apparently no way to load freight into its AeroLiner trailer. If it were legalized and orders were in hand, MAN and Krone could have such a rig ready for sale in three or four years, a MAN spokesman said.

The trailer's rear door is fixed, a Krone representative said, although MAN's statement said it was operable and its floor would match existing loading "ramps." A lift gate is tucked into the trailer's rear below the floor.

The AeroLiner trailer's lower rear also sports a sizeable digital readout that could inform following motorists of traffic conditions ahead and of the truck driver's intentions. The Concept S tractor has large wheels and very low-profile tires that would presumably offer low rolling resistance. Cameras rather than mirrors give a driver views to the rear, or would if the tractor were ready for the road.

The rig's streamlining and its teardrop shape contrasts sharply with tractor-trailers now on Europe's roads, the MAN statement said.

"The rectangular block form of today's trucks is accounted for by the need for maximum utilization of the space available within the statutory limitation imposed on the length of road trains at 16.5 meters," it lamented.

"The innovative truck-trailer combination makes it possible to tap into considerable aerodynamic potentials. To this end, however, tractor and trailer have to be somewhat longer, towards both front and rear.

"This is in order to realize the more streamlined front end of the vehicle with its rounded radiator as well as the aerodynamic rear end, while keeping the loading capacity the same."

In other words, the trailer narrows towards its rear, so needs to be longer to keep the same volume as a squared-off body. Thus the aero rig measures 18.82 meters, or 61.75 feet. This is 2.3 meters or about 7.5 feet more than is now allowed.

Anders Nielson, who heads MAN Truck & Bus, emphasized the potential to reduce emissions of CO2, a greenhouse gas that is believed to contribute to climate change. EU authorities are expected to limit CO2 as their American counterparts already have. Reduction in fuel use corresponds directly to cuts in CO2.

"Politicians could achieve big gains in environmental protection with a minor change to the law while simultaneously utilizing the innovative strength of Europe's commercial vehicles industry," Nielsen said.

The EU Commission is considering a lengthening of the tractor cab as well as the rear end of the vehicle in a proposed directive due out at the beginning of 2013, the MAN statement added.

Daimler Trucks, which built the M-B Actros tractor that powers the Aerodynamics rig shown at IAA, said the EU proposal is for an additional 500 milimeters or 19.7 inches for aero improvers at a trailer's rear. This would be enough for the Mercedes-Schmitz concept to legally operate, though it wouldn't look as spectacular as the MAN-Krone rig.