Studies are underway in JAMA on appropriate static (height of head restraint and backset) and quasi-dynamic (dynamic head rotation angle of Hybrid III dummy and dynamic backset) seat & head restraint evaluation methods for assessing whiplash-associated disorders in rear impacts. For various types of seats, the following items were evaluated for each index: i) road accident & whiplash phenomena, ii) reproducibility and repeatability, iii) correlation with dynamic evaluation results on BioRID II, iv) suitability for various seat types. The results revealed new findings as follows:
- As for height of head restraint, if the height of head CG + ramping up is secured, a further increase in height does not provide much support for reducing injury.
- As for backset, due to poor reproducibility in measurements on conventional HRMD, a new measuring method on the basis of SRP is effective. A decrease in backset reduces injury, however, since an excessively small backset impairs comfort, the balance between safety and comfort was examined.
- As for dynamic head rotation angle of the neck of the Hybrid III dummy, because of poor biofidelity of the dummy, the angle is not considered to be good for a proper dynamic evaluation, however, thanks to good reproducibility and repeatability of the dummy as well as some correlation between head rotation angle and injury criteria, the angle can be used as a tool for alternative evaluation of the backset.
- The dynamic backset was proposed as an alternative test to the static backset. However, the evaluation uses only the neck behavior of the dummy, and reproducibility and repeatability are still low. Consequently, the backset is not regarded as an appropriate evaluation method at this time.