Interpretation ID: nht92-9.25

DATE: February 4, 1992

FROM: Douglas Kubehl -- Technician, Safety Engineering Associates, Inc.

TO: Paul Jackson Rice -- Chief Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 3/16/92 (est) from Paul Jackson Rice to Douglas Kubehl (A39; Std. 209)

TEXT:

As an engineer, I have been asked to obtain a legal translation of FMVSS Part 571.209, which I have enclosed for your reference. Specifically, my interest lies in the wording of parts 209-S4.4 and 209-S5.3.

In 209-S.4.4a(1), it is clearly stated that a loop force of 5000 pounds is required to produce a force of 2500 pounds on each structural component. However, part 209-S4.4b(4) seems to be a bit ambiguous. It states: "The length of the pelvic restraint between anchorages shall not increase more than 20 inches or 50 centimeters when subjected to a force of 2500 pounds". My interpretation of this statement is that one must employ a loop force of 5000 pounds to achieve 2500 pounds of force on each component, as specified in S4.4a(1). I am concerned that one could misinterpret the above statement as requiring a 2500 pound loop force, rather than the intended value of 5000 pounds.

Part 209-S5.3a, which addresses the performance of the belt assembly, refers to Figure 5 and requires a tensile force of 2500 pounds. It goes on to say that this force is equivalent to a 5000 pound force being applied to an assembly loop. Figure five is referred to several times throughout the passage, each reference requiring a specific force. Again, because the relationship of the tensile force to assembly loop force is not explicitly stated, we are concerned that one may mistake the tensile force to be the total loop force applied.

We have previously addressed this question to John Lee of NHTSA's enforcement division. Mr Lee indicated that as per enforcement testing, part 209-S4.4b(4) requires a 5000 pound loop load. When asked for a written confirmation/interpretation, Mr. Lee referred us to your office.

We look forward to your response regarding appropriate interpretation. Thank you for your attention in this matter.