FMVSS 202a and the head restraint gtr specify a dynamic sled test with Hybrid III dummy as an alternative to static tests. However, the poor biofidelity of Hybrid III dummy and the evaluation method based on the neck rearward rotational angle of the dummy during rear impact are urgent issues. To solve these issues, a dynamic evaluation of OC-T1 displacement, corrected for the seat back rearward inclination (hereinafter called “dynamic backset”), using BioRID II which has superior biofidelity, was studied to establish a test method with higher effectiveness, repeatability and reproducibility.

From dynamic Backset evaluations by dynamic tests and simulations using IIWPG crash pulse on various types of seats and analysis of real world minor neck injuries involving such seats in Japan, the following new facts were found. (1) Dynamic backset can evaluate the effectiveness of various types of seats with whiplash mitigation features, such as reactive, passive, and WHIPS, more accurately than neck rearward rotation of Hybrid III. Since the seat effectiveness increases as dynamic backset decreases, it is appropriate for a dynamic evaluation parameter as an alternative of static backset tests. (2) By setting each seat back to its design torso angle, instead of 25 degrees for every seat, the variation in BioRID II installation is decreased, resulting in higher repeatability and reproducibility. (3) According to the correlation analysis among real world accidents, minor neck injury phenomena, and various evaluation indicators, reduction of dynamic backset has an inhibitory effect on occurrence of minor neck injuries. (4) Confirming the relationship between other injury criteria