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Engineering with Uncertainty: Monitoring Air Bag Performance


Modern engineering is complicated by an enormous number of uncertainties. Engineers know a great deal about the material world and how it works. But due to the inherent limits of testing and the complexities of the world outside the lab, engineers will never be able to fully predict how their creations will behave. One way the uncertainties of engineering can be dealt with is by actively monitoring technologies once they have left the development and production stage. This article uses an episode in the history of automobile air bags as an example of engineers who had the foresight and initiative to carefully track the technology on the road to discover problems as early as possible. Not only can monitoring help engineers identify problems that surface in the field, it can also assist them in their efforts to mobilize resources to resolve problem.

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  1. The history of air bags has been marked with numerous complications and disagreements [5, 6]. By the late 1980s there was broad consensus that the technology should be installed in most (if not all) vehicles, but engineers have had to struggle with competing ideas of how air bags should be designed and the role they should play in automobile safety.

  2. The question of whether to design air bags for people wearing seat belts or for people otherwise unrestrained has been a source of significant controversy through the history of the technology [5, 6]. NHTSA regulations, however, have required since the 1980s that air bags be tested with unbelted 50th percentile male dummies in an effort to ensure they provide some benefit to unbuckled occupants [10].

  3. A number of news sources reported that these burns were the result of the chemicals used to inflate the bags, but most engineers ultimately concluded that they were caused by the high temperatures of the gases, not the chemical makeup of the materials.

  4. Air bags were credited with saving 1500 lives in early 1997 [47, p. 832]. As of January 2008, air bags were credited with saving over 25,000 lives in the United States [48].

  5. More recent research has shown that these depowered bags not only made them safer for small women and children, but actually lowered the risk of driver death across the board [53].

  6. The code of ethics of nearly every professional engineering society includes this as one of the foremost responsibility of engineers [57].


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The author would like to thank Deborah Johnson and two anonymous reviewers for their very useful suggestions for this paper. The research for this article was supported by the Department of Science, Technology & Society at the University of Virginia, National Science Foundation Research Grant SES-0080600, and the Dwight David Eisenhower Transportation Fellowship Program.

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Correspondence to Jameson M. Wetmore.

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Wetmore, J.M. Engineering with Uncertainty: Monitoring Air Bag Performance. Sci Eng Ethics 14, 201–218 (2008).

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  • Engineering
  • Uncertainty
  • Monitoring
  • Risk
  • Social experiment