Interpretation ID: nht81-2.30

DATE: 06/01/81

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: British Standards Institution

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your letters concerning section 4.2(d) of Standard No. 209, Seat Belt Assemblies. Section 4.2(d) provides that after seat belt webbing has been subjected to an abrasion test, it must have not less than 75 percent of the strength of the unabraded webbing set in section 4.2(b) of the standard. You pointed out that section 5.2(d) is inconsistent with section 4.2(d). As explained below, section 4.2(d) correctly states the requirement intended by the agency and section 5.2(d) needs to be corrected.

The abraded webbing strength test procedure set forth in section 5.2(d) of the standard is incorrect. It specifies that the median value of the breaking strengths of the abraded and unabraded webbing are used to determine the percentage of breaking strength retained. Such a test procedure unfairly penalizes a manufacturer that produces webbing with an unabraded breaking strength far in excess of the requirements specified in section 4.2(b).

For example, section 4.2(b) specifies that Type I webbing is to have a breaking strength of 6,000 pounds. Assume that the unabraded webbing has a median breaking strength of 8,000 pounds and the abraded webbing has a median breaking strength of 5,600 pounds. The median breaking strength of the abraded webbing is substantially more than 75 percent of the 6,000 pound breaking strength specified in section 4.2(b). However, the median abraded breaking strength is only 70 percent of the median unabraded breaking strength.

The agency intends to modify the standard so that the abraded webbing strength test procedure specifies that the median breaking strength of the abraded webbing is compared to the breaking strength specified in section 4.2(b) to determine the percentage of breaking strength retained.

Sincerely,

ATTACH.

British Standards Institution

JANUARY 6, 1981

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

Dear Sirs

FMVSS

Many thanks for your letter of 12 December 1980 on the above subject.

You say in your letter that Standard Number 209 requires abraded webbing in manual belt systems for use in motor vehicles to have not less than 75% of the strength of unabraded webbing.

Clause @ 4.2(b) at the end states 'the median value shall be used for determining the retention of breaking strength in paragraphs (d), (e) and (f) of this section'.

Clause @@ 4.2(d) states that 'after abrasion, the webbing shall have a breaking strength of not less than 75% of the breaking strength listed in @@ 4.2(b). For clarity surely this should read - not less than 75% of the median value obtained during tests to clause @@ 4.2(b)'.

I would appreciate your comments.

Yours faithfully

J E BINGHAM SENIOR TEST ENGINEER

British Standards Institution

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

Dear Sirs

FMVSS - 209 SEAT BELT ASSEMBLIES

Clause 5.1 (b) reads . . . . the median value shall be used for determining the retention of breaking strength in paragraphs (d) (e) and (f) of the section.

Clause 4.2(d) reads . . . . shall have a breaking strength of not less than 75% of the breaking strength listed in Clause 4.2(b) for that type of belt assembly.

Please clarify the level to which the webbing strength after abrasion is to be compared. Is it:-

1. 75% of median breaking strength found under clause 5.1(b) or

2. 75% of minimum breaking strength listed in clause 4.2(b)

I have written to you on this subject before and would appreciate a speedy reply.

Yours faithfully

J E BINGHAM -- SENIOR TEST ENGINEER, MOTOR VEHICLE SAFETY COMPONENTS SECTION