Interpretation ID: nht72-3.33

DATE: 03/15/72

FROM: AUTHOR UNAVAILABLE; Robert L. Carter; NHTSA

TO: Society of Automotive Engineers, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of February 7, 1972, to the Administrator, in which you requested "clarification" of two requirements of Standard 207 that impose forces on rearward facing seats.

We do not believe that the requirements are unclear. S4.2(b) requires a rearward facing seat to withstand a force of 20 times its weight applied in a rearward direction, while S4.3.2.2 requires the restraining device not to release or fail under an acceleration of 20 g's in the direction opposite to that in which the seat folds.

You suggest that these forces and accelerations are equivalent to those in a 30 mph barrier impact, and point out that none of the existing standards provides for a 30 mph rear impact. The intent of the cited sections is to require rear facing seats to withstand the force of rear and collisions, which occur frequently and are often of considerable severity. We have some doubt that the 20 g acceleration is equivalent to a 30 mph rear barrier impact; frontal 30 mph impacts typically produce accelerations of 30 to 40 g's. Whether it is not is irrelevant, however, to the validity of the standard. The standard is clear in its own terms, and in our judgement its requirements are appropriate and feasible.