Interpretation ID: nht81-2.45

DATE: 07/07/81

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: British Standards Institution

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your letter of March 12, 1981, concerning the strength requirements specified in Safety Standard No. 209, Seat Belt Assemblies, for a dual buckle (i.e., a two buckle unit) anchored in a vehicle by one common anchorage attachment.

As explained below, I disagree with your judgment that the standard does not deal adequately with the dual buckle design. Your proposal to test the dual buckle with 5,000 pounds of force is also incorrect; the correct force is 6,000 pounds.

Section 3 of the standard defines "hardware" as "a metal or rigid plastic part of a seat belt assembly." That section further defines "attachment hardware" as "any or all hardware designed for securing the webbing of a seat belt assembly to a motor vehicle." As described in your letter and shown in its attached photograph, the dual buckle has a common metal anchorage attachment. Since the purpose of that metal part is to secure the webbing to the vehicle, it is considered attachment hardware.

Section 4.3 (c)(2) specifies that "attachment hardware designed to receive the ends of two seat belt assemblies shall withstand a tensile force of at least 6,000 pounds or 2.720 kilograms without fracture . . . ." Since the common anchorage attachment is designed to receive the force created by the ends of two seat belt assemblies, it must meet the requirements of S4.3(c)(2).

You are correct that the attachment bolt is required to withstand a force of at least 9,000 pounds or 4,080 kilograms under paragraph S4.3(c)(1) of the standard.

Sincerely,

MARCH 12, 1981

F. BERNDT, CHIEF COUNSEL -- U.S. Department of Transportation, NHTSA

Dear Sirs,

FMVSS 209

We have been asked to test for FMVSS approval a Dual Buckle anchored in the vehicle by one bolt, the Dual Buckle having common anchorage attachment.

The standard does not cope fully with this design and I suggest that it is tested in the following manner. The Dual Buckle should be tested statically at 5000 lbs and survive this test. This test would be in addition to the loop load test. The anchorage bolt would be tested to 9000 lbs. I have chosen 5000 lbs as a test limit for the following reason. The loop load test is done at 5000 lbs, the attachments being subjected to a load of 2500 lbs during this test. To prove the dual buckle we need to test it statically at twice this load of 2,500 lbs i.e. 5,000 lbs.

I would appreciate your comments on my proposal.

I have also written this letter to Mr A Cardarelli of AAMVA.

Yours faithfully

J E BINGHAM -- MOTOR VEHICLE SAFETY COMPONENTS SECTION, BRITISH STANDARDS INSTITUTION

(Photo Omitted)