Mr. Robert E. Norton II
Senior Staff Counsel
Daimler Chrysler Corporation
1000 Chrysler Drive CIMS 485-13-62
Auburn Hills, MI 48326-2766
Dear Mr. Norton:
This responds to your letter dated March 12, 2003, in which you inquire about the requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 209, Seat belt assemblies. You ask if there are objective criteria to evaluate compliance with the requirement under the second sentence of S4.1(e) of FMVSS No. 209 that a "[b]uckle release mechanism shall be designed to minimize the possibility of accidental release." As explained below, compliance with S4.1(e) requires viewing that provision of the standard in the context of FMVSS No. 209 as a whole.
In your letter, you question how the agency would evaluate compliance with this provision of S4.1(e). You state that if the provision is read in the context of the entirety of FMVSS No. 209, then compliance with the "accidental release" requirement could be demonstrated by satisfying the performance requirements of S4.3(d)(3) of FMVSS No. 209, which refers to a test procedure set out in S5.2(d)(3). In the alternative, you contend that if compliance with S4.1(e) cannot be ascertained using this test procedure, then this provision of S4.1(e) would be invalid for lack of objective test procedures.
The S4.1(e) requirement that a seat belt buckle be designed to minimize the possibility of accidental release during an impact must be viewed as part of FMVSS No. 209 as a whole. FMVSS No. 209 requires, among other things, that seat belt buckles meet minimum performance and material requirements. S4.3(d)(3) establishes criteria to address accidental release, stating that:
The buckle of a Type 1 or Type 2 seat belt assembly shall not release under a compressive force of 1779 N applied as prescribed in paragraph S5.2(d)(3). The buckle shall be operable and shall meet the applicable requirement of paragraph S4.4 after the compressive force has been removed.
Under the test procedure in S5.2(d)(3), a curved cylindrical bar is used to apply the compressive force to the buckle.
S4.3(d)(3) was added to FMVSS No. 209 to "eliminate buckle designs that are prone to accidental damage, or that release during the initial phase of the accident." 36 Federal Register 4607; March 10, 1971. S4.3(d)(3) provides an objective standard for minimizing accidental release during an impact, thus providing objective criteria for the requirement under S4.1(e). S4.3(d)(3) does not address accidental release not associated with a crash. Although we recognize that the "accidental release language of S4.1(e) could be read broadly to cover various scenarios, for compliance purpose, we interpret it to only refer to accidental releases that might occur during a crash. Non-crash accidental releases are not regulated by FMVSS No. 209, notwithstanding the arguably broader language of S4.1(e), as the only test procedure designed to address accidental release utilizes a force level much greater than would be contemplated in a non-crash environment.
In an August 31, 1976, letter to Volvo, the agency stated that for buckles unlikely to be damaged by compressive forces in a crash, the requirements of S4.3(d)(3) would not be applicable. While the Volvo letter stated that the original motivation for adopting this requirement was to guard against possible damage to a buckle caused by the steering wheel in a crash situation, the language of the requirement is broad enough to guard against other potential compressive forces as well, as evidenced by the fact that the requirement is not limited to buckles in the seating position with a steering wheel. In response to the notice that proposed extending the crush release requirements to all Type 1 and Type 2 seat belts, commentors did request that the requirement only be made applicable to buckles that could contact the steering wheel. (See comments from Britax and Irvin Industries, Inc. at Docket No. 69-23.) However, the agency did not amend the requirement to limit it to that narrower purpose. Accordingly, any current or future buckle with the likely potential to experience any compressive force during an impact would be required to comply with S4.1(e) and S4.3(d)(3), as tested under S5.2(d)(3).
I hope this addresses your concern. If you have any further questions please contact Mr. Chris Calamita of my staff at (202) 366-2992.
Stephen P. Wood
Assistant Chief Counsel
for Vehicle Safety Standards and Harmonization