Scott Willard, Regulatory Analyst
Seating Systems Division
21557 Telegraph Road
Southfield, MI 48034
Dear Mr. Willard:
This responds to your letter requesting an interpretation of paragraph S5.3.4 of Federal Motor Vehicle Safety Standard (FMVSS) No. 202a, Head restraints; Mandatory applicability begins on September 1, 2008. Specifically, you asked for clarification with regard to what is the lowest position of adjustment for a head restraint. Based on the information you have provided and the analysis below, we have concluded that, for the design you ask about, the lowest position of adjustment refers to the position in which the head restraint is in contact with the top of the seat back.
By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture.
You noted in your letter that Head restraint design often allows adjustment travel below the lowest locking position because contact with the seat back serves as the stop for the lowest position. You stated that this is not considered a stowed position, but that usable head restraint adjustment travel includes this distance and may [a]ffect the determination of the mid-travel locking position chosen for the dynamic test. You asked whether the lowest position of adjustment under S5.3.4 was a locked position slightly above contact with the top of the seat back, or below that position, in contact with the top of the seat back.
S5.3.4 of FVMSS No. 202a reads, in relevant part, as follows:
At each outboard designated seating position, .If the head restraint is adjustable, adjust the top of the head restraint to a position midway between the lowest position of adjustment and the highest position of adjustment. If an adjustment position
midway between the lowest and the highest position does not exist, adjust the head restraint to a position below and nearest to midway between the lowest position of adjustment and the highest position of adjustment.
We interpret the phrase lowest position of adjustment to mean, for the design you ask about, the position where the head restraint is in contact with the top of the seat back. Most head restraint adjustment positions are the places where the head restraint locks or clicks into a detent. However, for designs where the head restraint may be adjusted below the lowest locking position, the position where the head restraint contacts the top of the seat back would be an adjustment position, even though it does not click into a detent at that point. The seat back provides a stop for the downward adjustment of the head restraint, just as a detent does at other positions of adjustment. Additionally, we note that many people leave or position the head restraint at this point. Therefore, we consider it the lowest point of adjustment for purposes of determining the mid-travel locking position for the dynamic test.
If you have any further questions, please do not hesitate to contact Rebecca Schade of my staff at (202) 366-2992.
Anthony M. Cooke