Researchers have determined that airbags and antilock braking systems do not reduce the likelihood of accidents or injuries because they may encourage more aggressive driving, thwarting the potential benefits of such safety features.The behavior responsible for this seeming paradox is called the offset hypothesis, which predicts that consumers adapt to innovations meant to improve safety by becoming less vigilant about safety, said Fred Mannering, a professor of civil engineering at Purdue University.
So says a September 27, 2006 press release issued by Purdue University. The study to which it refers will be published in The Journal of Risk and Uncertainty, or so they (its authors) say.(Thanks to investigator Steve Nadis for bringing this to our attention.)