Interpretation ID: nht75-6.26

DATE: 06/02/75

FROM: JAMES B. GREGORY -- NHTSA ADMINISTRATOR

TO: DAVID E. MARTIN -- DIRECTOR AUTOMOTIVE SAFETY ENGINEERING GENERAL MOTORS CORPORATION

TITLE: N40-30

TEXT: Dear Mr. Martin:

This responds to your December 17, 1974, and March 31, 1975, letters asking whether your proposed inertia seatback latch meets the requirements of Federal Motor Vehicle Safety Standard No. 207, Seating Systems.

After carefully examining the mechanism, considering General Motors' arguments in its favor, and meeting twice with GM representatives, we have decided that the proposed inertia latch would not comply with S4.3.1 of FMVSS 207 unless an emergency release were added to enable someone to override the automatic locking mechanism when necessary.

We agree with GM that the proposed seatback latch is an improvement in some respects over current designs. The latch provides added convenience for rear seat occupants since under normal circumstances they may fold the seat forward by simply pushing on the seatback. We also recognize that there may be a safety advantage in certain circumstances requiring fast exit from the vehicle in that the passenger will not have to fumble for a latch, which, though readily accessible, is neither in the same location nor operated in a similar manner in all cars. Your proposed design also avoids a serious problem of some current latches: namely, that they will not release if even light pressure is applied against the seatback in a forward direction. The National Highway Traffic Safety Administration is seriously considering action on this problem.

Despite these advantages, GM's proposed inertia latch would satisfy neither the intent nor the wording of S4.3.1 of FMVSS 207 because it would not release when the vehicle is upside down or upright at a pitch attitude exceeding a 32% downgrade. Such vehicle positions are not uncommon in accident situations and GM's own figures indicate that "100 rear seat occupants per year could be hindered in leaving the vehicle under circumstances which would make prompt egress important." S4.3.1 requires that "the control for releasing the (self-locking seatback) device shall be readily accessible to the occupant of the seat . . . and . . . to the occupant of the designated seating position immediately behind the seat." Under normal conditions the seatback itself would be the control for your latch and it is certainly readily accessible. When the vehicle is nose down or inverted, however, the seatback would not perform this function and there would consequently be no readily accessible control for releasing the self-locking device.

Because it is often important for passengers in post-accident situations immediately to leave or be removed from a vehicle, for any number of reasons including fire, serious bleeding or hazardous vehicle location, it seems especially important that a seatback release control operate under these circumstances. Adding an emergency latch lock override to the inertia latch design would avoid this problem while retaining the previously mentioned advantages of your design.

Sincerely,