Interpretation ID: nht81-3.37

DATE: 11/12/81

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Dayton T. Brown, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your recent letter requesting an interpretation of paragraph S4.4(b)(3) of Safety Standard No. 209, Seat Belt Assemblies, as it applies to a continuous-loop, Type 2 seat belt assembly. You ask whether each structural component of such a seat belt assembly should be considered "common" hardware for both the pelvic and upper torso portions of the assembly.

Paragraph S4.4(b)(3) of Standard No. 209 specifies that the structural components in a Type 2 seat belt assembly that are common to pelvic and upper torso restraints shall withstand a force of not less than 3,000 pounds. Arguably, in a continuous-loop system with a sliding buckle latchplate, every component of the assembly could be considered "common" hardware since, as your letter points out, if one of the components should fail, the entire assembly could be rendered useless. However, the agency has stated in the past that testing for compliance with paragraph S4.4 of the standard on continuous-loop, Type 2 assemblies will be conducted by using a webbing clamp to segregate the portion of the assembly not being tested, i.e., to separate the pelvic and upper torso portions. This means that in continuous-loop systems the pelvic portion and the upper torso portion are not to be tested simultaneously. Although a test apparatus can be designed to simultaneously load a Type 2 continuous-loop assembly without the use of webbing clamps, the agency determined that such a test method is extremely difficult to perform. I am enclosing copies of two earlier letters of interpretation on this subject.

In light of this prior interpretation, the agency cannot conclude that all components of a continuous-loop system are "common" hardware for purposes of S4.4(b)(3). Rather, it is our opinion that only the latchplate, buckle and the inboard seat belt anchorage are common hardware for purposes of S4.4(b)(3). The belt retractor and the "D" ring should be considered only part of the upper torso portion of the continuous-loop system.

I would point out that it is up to the vehicle manufacturer to determine and certify compliance with all applicable safety standards under the National Traffic and Motor Vehicle Safety Act. The agency does not provide prior approval of any safety design or test method. Therefore, you are free to test seat belt assemblies by any method you believe to be sufficient to establish due care that the assemblies are in compliance with Safety Standard No. 209. In our opinion, however, the test method mentioned in your letter would maintain a somewhat higher standard of performance than that currently required by the standard.

Sincerely,

ATTACH.

SEPTEMBER 3, 1981

Office of Chief Council -- National Highway Traffic Safety Administration

Gentlemen:

I am requesting an interpretation of paragraph S4.4(b)(3) within Federal Motor Vehicle Safety Standard 209, Seat Belt Assemblies.

The referenced paragraph pertains to the structural loading of the "common" hardware within a type 2 seat belt assembly.

We have always tested the buckle tongue and buckle assemblies as common hardware. My concern is, with a type 2, one retractor assembly which has a free sliding buckle tongue. I feel that each structural component within the assembly (e.g., the retractor, the sling or "D" ring) could be considered common to both the pelvic and torso portions, due to the fact if one of the components should fail, the entire assembly would be rendered useless.

One possible argument to my feelings would be, that during the actual dynamic crash environment as opposed to the static loading environment of the standard, there may not be sufficient time for all of the loads to be evenly distributed.

The reason for my request, is that Dayton T. Brown, Inc. conducts certification testing for various seat belt manufacturers. We do not want to overburden them by insisting that all of their components meet the common hardware requirements, nor do we want to jeopardize the integrity of the system by not fully testing it.

Very truly yours, DAYTON T. BROWN, INC.;

D. R. Wachsmuth -- Senior Test Engineer

cc: D. Delve NEF32 -- NHTSA