The Airbag Two Decades Later

By Jack R. Nerad

There was a time when the automotive airbag was as hotly debated as the contribution by humans to global warming is today. Three decades ago, many safety advocates were gung ho to introduce the airbag, but most automobile manufacturers fought the idea, fearing that extra cost of the airbags plus potential misfires would decrease profits. And some auto safety engineers were concerned that the installation of airbags would discourage drivers and passengers from using safety belts, the most effective kind of safety restraint.

The debate raged for a decade before Secretary of Transportation Elizabeth Dole, a Ronald Reagan appointee, issued a mandate in 1984 requiring airbags or automatically deployed seat belts in passenger cars beginning in 1990. This sent many companies scurrying to the drawing board and in many instances their solutions were the soon-to-be-much-hated motorized seatbelts that made entering a car a gymnastic exercise.

Fortunately, some car companies took another tack. One of the leaders was Volvo, which had helped establish its safety leadership position by, among other things, inventing the now-ubiquitous three-point seat belt. By the mid-Eighties, Volvo had worked with airbags and automatic seat belts for many years. As early as the 1970s, Volvo engineers experimented with airbags as a way of reducing fatalities, even producing a fleet of cars with airbags as part of their research.

As the U.S. Department of Transportation neared its recommendation on airbags and automatic seatbelts in 1984, Volvo established a project team of engineers, system developers and suppliers to begin its first Supplemental Restraint System (SRS) project. The term was chosen quite deliberately because Volvo and other manufacturers wanted to make it clear to consumers that the airbag systems are designed to supplement seat belts, not replace them. Throughout the process, analysis and component testing were implemented to minute detail. Volvo designed the shape and size of the crucial gas-generation tablets, which provide for proper gas production using a sodium azide (NaN3) chemical mix. A screen filter helped maintain a proper balance of gases and helped collect the inert, but very hot, residue within the gas generator, not in the bag itself where it could harm passengers who came in contact with it. Facilitating deployment of the apparatus, the company worked with the igniters and bags as well as the weavers of the fabric and the manufactures of the yarn.

Bosch, the supplier for the electronics, combined with Volvo to develop a unique piezo electric sensing device. Most mechanical sensors of the time were located in the bumper area. This new technology enabled a system where the sensor could be positioned inside of the vehicle under the driver's seat. The sensor mechanism was shorter and the cables and connectors were better protected. (Volvo uses much the same concept today, but the sensor is now positioned behind the gearshift lever.) Volvo rolled out its airbag-fitted production model in 1987, three years ahead of U.S. law.

Automotive airbags quickly became a successful safety device, but they also gained some negative publicity when some children and smaller adults were killed by airbag deployments, some in non-life-threatening situations. In 1999, Volvo continued to lead the field by installing a new generation of airbags that addressed that issue. These devices, now known in the industry as "smart airbags," sense such things as body weight, speed at impact and impact angle, to adjust the force of airbag deployment automatically. These "smart bags" offer yet another level of protection above conventional bags by automatically sensing when to step down the force of impact, thereby reducing the risk to the vehicle's most important cargo -- the people riding inside the car. Volvo cars are currently equipped with a dual threshold system based on impact position relative to the part of the body being protected.

Airbag technology and the safety systems in general have evolved to not only include driver and passenger front airbags, but various forms of rear-seat passenger, side-impact and roll-over protection as well. These sophisticated systems constantly monitor a variety of data, preparing to protect the motorist for an impact which, in the life of most motorists, never occurs. But, because you never know when such an incident might occur, always buckle your seat belt.

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