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Interpretation ID: 22162ogm



    Mr. Mitsuhide Kikkawa
    Mazda North American Operations
    1500 Enterprise Drive
    Allen Park, MI 48101-2053


    Dear Mr. Kikkawa:

    This in response to your September 12, 2000, letter regarding the provisions of Standard No. 201, "Occupant protection in interior impact," as they relate to convertible roof frames and roof linkages. In your letter, you observe that S6.3(a) of Standard No. 201 exempts certain convertible roof frame and roof linkage components from the requirements of Standard No. 201 and ask several questions about these exemptions in relation to both the soft-top and removable hard top versions of the Mazda Miata.

    You ask a number of questions relating to the application of Standard No. 201 to the soft-top version of the Miata. Your letter describes the Miata as having a movable convertible roof linkage with a locking system on the roof frame that engages fixed anchorages located at the junction of the A-pillar and the front header. You ask if the fixed anchorages located at the junction of the A-pillar and the front header are exempt from the impact requirements of Standard No. 201 by operation of the exemption contained in S6.3(a). You then ask, in the event these fixed anchorages are exempt, if the A-pillar reference point (APR) were located on the anchorage, if the target area known as A-pillar 1 (AP1) would have to be relocated. Based on Mazda's review of Standard No. 201 and its history, it is your company's belief that the fixed anchorages are exempt from the requirements of Standard No. 201 and that AP1, which is located on the anchorage, would not have to be relocated.

    The agency agrees. S6.3(a) of Standard No. 201 provides that a vehicle need not meet the requirements of S6.1 through S6.2 for any target located on a convertible roof frame or a convertible roof linkage mechanism. "Convertible roof frame" is defined in S3 as the frame of a convertible roof. "Convertible roof linkage mechanism" is defined in S3 as any anchorage, fastener, or device necessary to deploy a convertible roof frame. The definition of anchorage does not distinguish between fixed and movable anchorages.

    The issue of what constitutes a convertible roof frame and a convertible roof linkage was addressed several times during the development of Standard No. 201. In a response to petitions for reconsideration published in the Federal Register on April 8, 1997 (62 FR 16718), the National Highway Traffic Safety Administration (NHTSA) discussed the issue of whether anchorages should be considered to be part of a convertible roof linkage for the purposes of S6.3(a). At that time, the agency indicated that the definition of convertible roof linkage mechanism should not be limited to components on the roof itself and includes anchor points on the front header and/or A-pillar for the convertible roof. The agency's position in regard to anchorages reflects its view at the time when the head impact protection requirements were established. The preamble to the final rule establishing the upper interior head impact provisions - published in the Federal Register on August 18, 1995 (60 FR 43031) - indicated the agency's view that countermeasures would not be feasible on convertible roof frames and linkage mechanisms because the presence of a countermeasure such as padding would interfere with their movement. Therefore, NHTSA decided to exclude from the new requirements any target that would be located on those components. While fixed anchorages were not mentioned at that time, the agency believed then, as it does now, that it would not be practicable to require these anchorages to meet the performance requirements of Standard No. 201. As anchorages are exempt from the Standard's performance requirements, any target point located on such an anchorage is also exempt and would not have to be relocated.

    In addition to your concerns regarding anchorages in soft-top convertibles, you also ask if a test conducted against a valid target point in soft-top convertible would be rendered invalid if the free motion headform (FMH) struck a portion of a convertible roof frame after striking a valid target point. In the case where such a secondary impact occurs, and the resulting HIC values from that secondary impact exceed those allowed by Standard No. 201, Mazda believes that the test should be deemed to be invalid. In support of this view, you refer to a February 19, 1999, letter to Mr. George Parker of the Association of International Automobile Manufacturers in which NHTSA indicated that secondary impacts with fixed glazing would render a test invalid. In that case, the agency indicated that where a secondary impact with glazing resulted in a noncompliant HIC score, NHTSA would disregard the test results on the basis that impacts with glazing are not within the scope of Standard No. 201.

    NHTSA agrees with your interpretation. As noted above, convertible roof frames are exempt from the requirements of Standard No. 201 as it is not practicable to install padding or other countermeasures on a convertible roof frame. As these frames are exempt from the requirements of the Standard, NHTSA will consider a test to be invalid in those instances where a secondary impact with a convertible roof frame results in a HIC score above that which is allowed by Standard No. 201.

    Your letter also asks a number of questions about the requirements of Standard No. 201 as they apply to detachable hard tops. According to your letter, the Mazda Miata is also available with a detachable hard top, and this top is secured to the front header through the use of the same anchorage and a similar latching system as are employed in the soft-top version of the Miata. You ask the agency to confirm your interpretation that

    the same considerations applicable to the latch and anchorages employed in a soft-top convertible would apply to the latches and anchorages used to secure a detachable hard top to the front header and A-pillar.

    As you indicate in your letter, NHTSA addressed the issue of detachable hard tops in the context of Standard No. 201 in response to a Petition for Reconsideration filed by ASC, Inc. in response to the agency's April 8, 1997, final rule (62 FR 16718). The ASC petition requested that the agency modify the definition of convertible roof frame to include hardtop convertibles - i.e., convertible tops that may be raised or lowered but are constructed of rigid folding sections rather than a cloth skin on a rigid frame. In rejecting that request, the agency noted that there did not appear to be any reason to exempt hardtop convertible roofs from the requirements of Standard No. 201 (see 63 FR 19839, April 22, 1998). In making this determination, NHTSA did not squarely address the issue of non-folding detachable hard tops or the linkages and hardware used to attach them to a vehicle. It is NHTSA's view that the considerations applicable to hardtop convertibles also apply to detachable hard tops. It is both reasonable and practicable to expect a detachable hard top to meet the requirements of Standard No. 201. However, NHTSA has not yet addressed the question of the latches and anchorages used to attach a detachable hard top to the front header of a vehicle. In the case of latches and anchorages, NHTSA believes that the installation of effective countermeasures to these components would be difficult at best and at worst would result in designs having little or no practical utility. Accordingly, NHTSA agrees with your view that latch and anchorage mechanisms for detachable hard tops are exempt under S6.3(a) of the standard.

    I hope that this is responsive to your inquiry. If you have any questions or comments, please contact Otto Matheke of this office at (202) 366-5253.

    Sincerely,

    John Womack
    Acting Chief Counsel

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