Effects of Air Bags on Severity Indexes for Roadside Objects

The effects of vehicle air bags on the severity of off-road, fixed-object crashes as indicated by the effect that the air bag has on severity indexes (SIs) for fixed objects were studied. In an earlier study, preliminary indications based on data from one state were that the presence of an air bag might reduce SIs for various fixed objects by 35 to 75 percent. This study extends that work by adding data from two other states and from additional crash years. Severe-injury SIs were developed for different roadside objects for two samples of late-model vehicles, one with air bags and one without. The states chosen for use in this effort were those in which injury could be linked to a specific object struck. The data also were chosen to reflect a newer vehicle fleet (i.e., vehicle year 1989 or later) and more recent crashes (i.e., those occurring between 1990 and 1994). Although there were some inconsistencies within classes of objects and between states, analyses indicated that the air bag appears to be related to decreases in the proportion of serious or fatal driver injuries of 10 to 30 percent for point objects such as trees and utility poles, 40 to 50 percent for guardrails, and 10 to 20 percent for other barriers. For many of the objects tested, the results were not statistically significant, probably because of the sample sizes available.