User adaptation to injury protection systems: Its effect on fatalities, and possible causes

Although it is generally believed that people drive less carefully when their vehicles are equipped with new protection systems, the possible impact of such behavior on fatalities has never before been quantified. A meta-study across a diverse set of injury protection systems strongly suggests that users do adapt to new protection systems in a way that increases fatalities, and that the effect is more intense for systems that are easily perceived by the user. Perceptibility was quantified and found to be higher for injury protection systems that require user activation; for these systems, it is estimated that about 9% of the fatalities can be attributed to adaptation.