We present a nontechnical discussion of changes made to the calculations of the lives saved by safety belts and air bags published by the National Highway Traffic Safety Administration (NHTSA). Each year when new data are available from the Fatality Analysis Reporting System, NHTSA’s National Center for Statistics and Analysis (NCSA) estimates the numbers of passenger vehicle occupants, ages 5 and older, that were saved by safety belts and air bags during that year. NCSA also estimates the number of people that would have been saved if belt use had been at various higher use rates.

Substantial changes are made to these calculations. They are corrected to properly recognize the combined effectiveness of safety belts and air bags, and to remove children under the age of 13 from the calculation of the lives saved by air bags. We examine the method currently used to parcel the total savings by belts and bags into those saved by belts and those by bags, and delineate the range of possible belt-bag attributions. Finally, we choose a consistent method for all calculations hypothesizing a higher belt use. Our choice will slightly change the interpretation of the number of lives that would have been saved if everyone had buckled up, but this change of interpretation is necessary to have consistent estimates.

The new methods will change some estimates substantially and so revisions will be issued for prior data years. We specify how these will be calculated. We also discuss the updated effectiveness ratings and belt use model that will be implemented simultaneously with the new methods.