Detailed sales data for head restraints in model years 1977-81 were acquired and studied. The results from the Texas, NCSS, NASS and FARS analyses were compared to published statistical studies of head restraints, including a major study of insurance claims. Laboratory and crash tests were reviewed, as were selected accident and injury case histories. The research, rulemaking and enforcement activities related to Standard 202 were discussed with Agency engineers and the public Docket was studied. The conclusions of this evaluation are based on all of the information sources - statistical, clinical and engineering.
Integral seats are significantly more effective than adjustable restraints.
The first conclusion is based on statistically significant findings from Texas and insurance claim files. The statistical findings, moreover are consistent with engineering intuition, clinical analyses and test results. As a result, it was necessary to rely on State data which do not explicitly distinguish whiplash from other injuries and which are suspected of reporting biases, especially for older cars. A major analytic effort was devoted to removing or minimizing the biases, so as to make the effectiveness estimates as accurate as possible. This effort resulted in some statistically complex estimates for which only approximate, rather than exact, confidence bounds were obtained.