An airbag for seat belts

The Beltbag, one of the highlights from the ESF 2009 Experimental Safety Vehicle, is due to go into production in a luxury-class model from Mercedes-Benz. The inflatable seat-belt strap is able to reduce the risk of injury to passengers in the rear in a head-on collision by lessening the strain placed on the ribcage.

Should the crash sensors detect a severe frontal impact, the airbag control unit will trigger deployment and inflation of the Beltbag. A gas generator then inflates the multi-layered belt strap with Velcro seams to nearly three times its normal width. The resulting larger surface area is able to better distribute the force acting on the seat occupant, thereby reducing the risk of injury.

The Beltbag can be used in exactly the same way as a conventional seat belt. The belt strap’s design is different from that of the standard belt though, and received top marks in practical trials for being extremely comfortable to wear and for its extra-soft belt strap edge.

“Mercedes-Benz is pursuing its safety initiative in the rear of vehicles with the Beltbag,” comments Prof. Dr.-Ing. Rodolfo Schöneburg, Head of Passive Safety and Vehicle Functions at Mercedes-Benz Cars. “After all, the excellent standard of safety offered by Mercedes-Benz doesn’t just apply to all model se-ries, but to all seats, too.”

Just like the active seat-belt buckle recently presented by Mercedes-Benz that is likewise earmarked for inclusion in a luxury model, the Beltbag was developed with a particular view toward new markets. There, the occupancy rate in the rear is as much as 30 percent, making it much higher than in Europe. By introducing the Beltbag, Mercedes-Benz is further expanding the safety system for passengers in the rear – in contrast to many other manufacturers, seat belts in the second row of Mercedes-Benz models already come equipped with belt tensioners and belt force limiters. It is not planned to introduce the Beltbag for the front occupants, as airbags are already included in the front on all models as a supplementary restraint system.

Because dummy measurement technology is not capable of quantifying the bene-fits resulting from a wider belt strap, such as the lower force exerted on occu-pants, the safety experts at Mercedes have also been working intensely with vir-tual human models, as such computer generated models make it possible to obtain detailed findings on the biomechanical strain during a collision.