Safety belt effectiveness in preventing fatalities to drivers isexamined versus a number of factors by applying the double pair coparison method to appropriate subsets of the fatal accident reporting system data. For each of 13 factors studied, safety belt effectivenesss (the % of fatally injured unbelted drivers who would not have been killed if they had been wearing safety belts) is estimated, as is an associated standard error of the estimate. The results, which are presented graphically, provide no evidence that safety belt effectiveness is systematically influenced by most of the factors investigated, includig car mass and model year. The absence of any systematic relationship with car mass is in agreement with an earlier finding based on the pedestrian fatality exposure method; this agreementadds plausibility to the assumptions used for both the earlier and the present methods. Safety belt effectiveness is greater for singlecar crashes than for crases involving 2 cars, this difference beingstatistically significant p less than .02. The results suggest weakly that safety belt effectiveness is greater for 2-door than for 4-door cars, and is greater for striking cars than for struck cars. Thedifferences probably reflect higher effectiveness in frontal (or rollover) crashes than in side impacts.
Abstract