Dr. Klaus Bs
Technology Center Allershausen
Am Ziegelwerk 1
Dear Dr. Bs:
This is in response to your December 12, 2007 facsimile, in which you asked about the head restraint position specification for the dynamic compliance option in Federal Motor Vehicle Safety Standard (FMVSS) No. 202a, Head Restraints. Specifically, you refer to a 2007 final rules elimination of the backset adjustment specification (while maintaining the up/down adjustment specification) in the dynamic compliance option for head restraints (72 FR 25484, May 4, 2007). You ask for clarification of how head restraints with adjustable backsets should be positioned for the dynamic compliance tests. As discussed below, the omission in the regulatory text of the language you referenced was an inadvertent error, and we plan to correct this error as a technical correction. This correction will clarify that head restraints with adjustable backsets can be tested in any position of adjustment during compliance tests for the dynamic option, i.e., the vehicle must comply in all such positions of adjustment.
FMVSS No. 202a seeks to reduce whiplash injuries in rear collisions, and in 2004 the National Highway Traffic Safety Administration (NHTSA) upgraded this standard to provide better whiplash protection for a wider range of occupants (2004 Final Rule). On May 4, 2007, NHTSA published a new final rule (2007 Final Rule) amending FMVSS No. 202a, which responded to petitions for reconsideration of the 2004 Final Rule (69 FR 74848, Dec. 14, 2004).
In your letter, you refer to the 2007 Final Rules elimination of the specification of backset adjustment in the dynamic compliance option for head restraints. Your letter asks for clarification of your assumption that the absence of specific instructions for backset adjustment must mean that head restraints with adjustable backsets should be adjusted midway between the most forward and rearward position of adjustment, analogous to the condition specified for the up/down adjustment of the head restraint (midway between the lowest and the highest position of adjustment). As explained below, your assumption is incorrect.
The 2004 Final Rule altered the head restraint position specification for the dynamic compliance option from any position of adjustment to a mid-height position and any position of backset adjustment. This was indicated in both S4.3 and S5.3:
S4.3 Dynamic performance and width. At each forward-facing outboard designated seating position equipped with a head restraint, the head restraint adjusted midway between the lowest and the highest position of adjustment, and at any position of backset adjustment, must conform to the following:
* * * * *
S5.3 Procedures for dynamic performance. Demonstrate compliance with S4.3 of this section in accordance with S5.3.1 through S5.3.9 of this section with a 50th percentile male Hybrid III test dummy specified in 49 CFR part 572 subpart E, with the head restraint midway between the lowest and the highest position of adjustment, and at any position of backset adjustment.
The 2007 Final Rule preamble did not discuss, and we did not intend to make any changes to the provisions of head restraint adjustment for this test. The omission of this test condition was an inadvertent error, and the agency plans on correcting this mistake in a forthcoming technical correction to the 2007 Final Rule. This will clarify that head restraints with adjustable backset can be tested in any position of adjustment during the dynamic compliance option.
If you have any further questions, please do not hesitate to contact Sarah Alves of my staff at (202) 366-2992.
Anthony M. Cooke