The seat belt is regarded as one of the most important inventions of the 20th Century, and has saved countless lives. It has been further improved with belt tensioners and belt force limiters, but that is not the end of its development: an innovative extension to the width of the belt, known as a Belt Bag, is able to reduce the risk of injury even fur-ther in an accident.

When a seat belt limits the movement of its wearer’s torso as intended during a collision, it subjects the body to considerable forces. The Belt Bag, on whose
development Mercedes-Benz is working intensively with the seat belt spe-cialist Autoliv, practically doubles its width within fractions of a second during an
accident. This increase in the width of the belt spreads the pressure over a wider area, thereby reducing the risk of injury. This is particularly beneficial for older passengers, whose ribcage is no longer so flexible.

As the name suggests, the Belt Bag is a combination of a seat belt and air-bag. When the crash sensors detect a serious impact, the airbag control unit activates the Belt Bag. A generator at the belt armature inflates the double-layered belt, which has Velcro seams. The volume of the Belt Bag is around four litres. The
developers consider the Belt Bag to deliver the greatest benefits in the rear of the car, where conventional airbags cannot be installed. It is therefore conceivable that the Belt Bag could be used here by Mercedes-Benz in the foreseeable future.