use of standardized anchor systems in motor vehicles and on child restraints. In its economic analysis, NHTSA quantified the costs and benefits of both rigid and flexible anchor systems, assessing two regulatory options that represented alternate approaches to complying with the final rule and a third option that it ultimately rejected.

To estimate the benefits of the rule, NHTSA combined data on deaths and injuries to children in seat restraints with data on the impacts of child restraint misuse from several sources, focusing on children ages zero to six. NHTSA made several modifications to these data, first adjusting for the number of injuries that would have occurred in the absence of restraints, then estimating the percent of all injuries associated with restraint misuse and the fraction of this misuse that would be eliminated by the anchor rule. The data on injuries and fatalities were reported by KABCO category, which classifies injuries based on the degree of incapacitation (killed (K), incapacitating injury (A), nonincapacitating injury (B), possible injury (C), and no injury (O)). NHTSA converted the estimates from the KABCO categories to the Abbreviated Injury Scale (AIS), using a standard algorithm that reflects the distribution of all crash-related injuries (not solely injuries to restrained children).

The AIS is a simple numerical system for ranking and comparing the severity of injuries based on the probability that the injury could be fatal. A score of 0 indicates that there were no injuries, whereas a score of 6 indicates that the injury was likely to be immediately fatal; intermediate scores of 1 through 5 indicate injuries of increasing threat to life. When multiple injuries occur, they are scored according to the most life-threatening injury; i.e., the Maximum AIS or MAIS. Examples of the types of injuries that fall into each category are provided in Chapter 2, Table 2-6.

To value these injuries, NHTSA applied its ELS approach, which first involves determining the costs and monetized QALY impacts for nonfatal injuries in each AIS category.15 See Box 2-4 for a description of the ELS approach. These monetary estimates are converted to ELS fractions by dividing the value for each injury category by the value of a fatality (estimated by NHTSA as roughly $3 million). These fractions are then multiplied by the number of injuries averted in each category and added to the number of fatalities, to determine the total ELS value for each regulatory option. The ELS values for each AIS category are calculated periodically based on data for all types of crashes nationally, then applied across the

15  

The QALY losses are based on an index adapted especially for crash-related injuries (Miller et al., 1991), rather than on one of the generic indexes used elsewhere in this case study.



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