Interpretation ID: aiam2749
P.E.
Volvo of America Corporation
Rockleigh
NJ 07647;
Dear Mr. Shapiro: This responds to your letter of December 20, 1977, enclosing a previou letter requesting an interpretation of paragraph S4.3(j) of Safety Standard No. 209, *Seat Belt Assemblies*. I am sorry that your earlier letter was misplaced.; Volvo is correct in its interpretation that the requirements fo emergency locking retractors in S4.3(j) (2) and (3) were promulgated for reasons of comfort and convenience, although this in turn is directed toward a safety objective. As you know, the more comfortable and convenient belts are, the more likely they will be worn by motorists. Further, the requirements in these paragraphs assure that the driver can make necessary movements in the occupant compartment safely.; Paragraph S4.3(j) (2) specifies that an emergency locking retractor >>>'shall not lock, if the retractor is sensitive to webbin withdrawal, before the webbing extends 2 inches when the retractor is subjected to an acceleration of 0.3g or less.'<<<; Volvo interprets this to require that the retractor not lock before th webbing extends 2 inches when the *webbing* is subjected to an acceleration of 0.3g. This is incorrect. The requirement specifically states that the *retractor* is to be accelerated. The agency does not agree that keeping the belt stationary and accelerating the retractor is equivalent to keeping the retractor stationary and accelerating the belt. This is due to the fact that inertial forces react upon the retractor during its acceleration that are not present when the webbing alone is accelerated. Therefore, results from the two methods of testing could differ significantly.; I hope this has been responsive to your inquiry, and if we can be o any further assistance please let us know.; Sincerely, Joseph J. Levin, Jr., Chief Counsel