Airbag development at Mercedes-Benz already began in 1966. The first driver airbag to reach production maturity was introduced in the 126-series S-Class in 1980. And the idea of a protective air cushion as a passive safety feature has by no means exhausted its potential, as an innovative rear airbag in the ESF 2019 shows. With belt-feeders, belt buckle illumination, USB belt buckles and belt heating, the ESF 2019 implements a number of ideas by which passengers on the rear seats might be motivated to wear seat belts using new methods.
The rear airbag has a special filling concept to inflate and position the air cushion. To this end it has an innovative tubular structure. In the event of a crash, cylindrical sections are rapidly inflated with compressed gas and form a framework – in a similar way to the new, inflatable tents where air hoses replace rods. But the really special feature of the airbags is the space between the bars of the framework. The side walls instantly capture the ambient air and retain it as the passenger's body sinks into the airbag. This gives the passenger support, and the loads acting on the head and neck vertebrae during a severe frontal impact can be reduced by up to 30 percent.
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 reboard position. The force is directed past the obstacle rather than against it.
How the seat belt wearing quota could be increased in the rear
Nowadays the driver and front passenger are protected by three-point seat belts as well as front airbags and sidebags in almost all series production cars. Three-point seat belts are standard for the rear seats. According to the Federal Highway Institute (BASt), the quota of rear seat passengers wearing seat belts in Germany has increased to almost 100 percent since this became compulsory in 1984. In some markets, however, the quota of rear seat passengers wearing seat belts is very low. If occupants in the rear seats are involved in an accident, the risk of injury is just as high as for those in the front seats. Moreover, rear passengers not wearing seat belts can be catapulted forward owing to the lack of restraint, and inflict severe injuries on front occupants who are wearing seat belts.
Accident researchers therefore consider it important to find new ways of motivating and encouraging rear seat passengers to fasten their seat belts. The ESF 2019 has a number of ideas for this:
- Belt feeder: this brings the belt within easy reach as soon as the door is closed. It is therefore more convenient to grasp.
- Belt buckle illumination: this makes it easier to find the belt buckle, and therefore easier to fasten the belt.
- USB belt buckle: this motivates the passenger to fasten the seat belt, as the USB connection is only enabled once this is done.
- Heated seat belt: motivates the passenger to fasten the seat belt, and can reduce belt slack because the heating effect of the belt close to the body allows passengers to dispense with thick jackets and coats. In addition, the heatable seat belt in combination with seat heating improves thermal comfort in the vehicle.