Last year, in the Experimental Safety Vehicle ESF, Mercedes-Benz presented the ideas the company's safety specialists are working on. Among the more than 20 innovations were near-series developments such as the rear airbag, which now becomes available as optional equipment in the S-Class with long wheelbase. The frontal airbag for the rear seat deploys particularly gently thanks to its innovative construction using a tubular structure. During severe frontal collisions, the rear airbag can considerably reduce the loads acting on the heads and necks of occupants on the outer rear seats.
The rear airbag uses an innovative concept to inflate and position the air cushion. To this end, is has a special tubular structure which is rapidly inflated by compressed gas from a cold gas generator. The space between is filled with ambient air. Patented valves ensure that the air is retained when the occupant is immersed in the airbag, creating the protective effect. The tubular structure itself has a content of approx. 16 litres. The effective volume of the space in between is up to 70 litres. The airbag volume is configured so that a rear occupant wearing a seat belt can be protected before contacting the front seats.
Designing a rear airbag for a frontal collision requires a different concept from a conventional driver or front passenger airbag. This is because the spatial parameters are different, occupant behaviour varies widely and the airbag must be accommodated in the adjustable backrest of the front seat. In addition, children and adults sit very differently in the rear of a vehicle.
Particular attention was therefore given to gentle deployment of the airbag in case people or objects are in the deployment zone. The special design of this new airbag decisively contributes to compliance with the in-house requirements of Mercedes‑Benz, some of which were derived from tests on front passenger airbags. The inflating tubes give way when contacting obstructions, e.g. a child seat in the rearfacing position. The force is directed mainly past the obstacle as of a certain counterforce rather than against it.
The airbag enhances the restraining effect of the belt system, and can support the head and neck to decrease the loads on them significantly. In combination with a beltbag, the inflatable seat belt and the seat cushion airbag of the Executive seat, the S-Class sets new standards for rear seat occupant safety.