Its performance was not spectacular, but it was rugged and reliable. Remember that the operation of such a safety system on a vehicle represents a legal liability situation of potentially catastrophic dimensions. Systematic failures of the system could lead to hundreds of deaths, which could lead to billions of dollars in legal costs. Last year, Ford had total profits of a couple of billion dollars on sales of a couple of million cars. One possible problem has been the tendency to deploy upon the encounter of a long, deep pothole.
Unnecessary deployment is somewhat dangerous, because it briefly incapacitates the driver.
In addition, it causes some expensive damage to the vehicle dashboard, and occasionally injures the driver. There have been numerous reports of hearing loss due to the abrupt change in pressure caused by deployment in a sealed car. Recent years have seen the evolution of the air bag systems in response to the need for more accurate detection of threatening situations. For some automakers, this has led to a desire for a sensor which measures all acceleration signals, instead of just a threshold, and allow signal processing to more accurately determine the need for deployment. The size of this market has stimulated several small sensor companies to develop and introduce micromachined piezoresistive accelerometers of the type studied in the last lecture.