Interpretation ID: nht72-1.45

DATE: 03/10/72

FROM: JAMES E. WILSON FOR CHARLES H. HARTMAN--NHTSA

TO: Rose Manufacturing Co.

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of February 1, 1972, concerning the National Highway Traffic Safety Administration (NHTSA) pamphlet, "What to Buy in Child Restraint Systems."

While you approve generally of the pamphlet, you state that you consider certain statements in it to be incorrect. Particularly, you disagree with two statements appearing on the page of the pamphlet discussing child harnesses. Those statements were: "Give preference to those which attach under the seat back, not over it."; and, "Give preference to those which either attach directly to the vehicle floor, or to the vehicle seat belt, not to the seat back." We do not agree that either of these statements is incorrect.

The NHTSA position is that child harnesses that attach over or directly to the vehicle seat back increase the chance of seat back failure, a hazard which you recognize in your letter. Our dynamic test data have shown that affixing a child harness in either of these ways can cause the inertial load of the child to be applied to the seat back excessively deforming or failing the seat back, thereby allowing excesive occupant excursion and increasing the chance of injury to the child. In short, these configurations increase rather than, as you seem to argue, decrease the chance of seat back failure.

With regard to the statements concerning compressive forces being applied to the child during a crash, while we agree in principle that such forces are undersirable, it is not clear from your letter how their application is prevented by having the child harness attach over the top of the vehicle seat. In any event, it is preferable, in our view, for some force to be applied to the child's torso, as long as it is evenly distributed, than to have the child flung into hostile surfaces within the vehicle.

We also do not agree with the statement on page 2 of your letter that harnesses can safely be attached to a vehicle seat back, as the seat back is ". . . in turn securely attached to the car floor." Our experience has been quite the opposite; vehicle seat backs are merely attached to the seat frame and are quite susceptible to collapse in crash situations.

Finally, we do believe the pamphlet, in its recommendation that a child should not stand on the front seat of the vehicle when the harness is attached, is consistent with the design of your harness in that both seek to reduce the danger of whiplash injury,

I hope this clarifies our position for you.

SINCERELY,

rose manufacturing co.

February 1, 1972

Douglas W. Toms Administrator National Highway Traffic Safety Administration U.S. Department of Transportation

Dear Mr. Toms:

Please permit us to congratulate you on the excellent pamphlet, entitled "What to buy in Child Restraint Systems".

Also, however, please permit us to question some statements in this pamphlet which we consider to be, in effect, erroneous and dangerous.

We refer to the next-to-the-last page regarding child restraint harnesses. The first drawing on this page illustrates a restraint harness essentially similar to the one we manufacture, and market under the "Sears" and other trade names. Your first statement in red ink states: "Give preference to those which attach under the seat back, not over it". We submit that any such harness which is attached solely under the seat back, and not also over it, is subject to two vicious hazards. First, it would in case of a crash permit the seat back to move forward to crush the child against the seat cushion. This might result from the folding forward of a hinged seat back or the breaking loose of a fixed one.

The second hazard is more prevalent and just as vicious. An adult lap belt is normally attached under the seat back, and is safe when thus attached. In a crash it puts the impact loading on the hips and pelvic region--the strongest parts of the body with no vital organs to be affected. This is positively not true of any belt or harness which places any restraint on the shoulders or upper torso. All adult 3-point belts are required to have the upper torso restraint attached at some point above the shoulder. Some such safety should also be required in the child harness. It must not be permitted to apply any compressive pressure to the shoulders and downward along the spine, in case of a crash.

Your second statement in red reads: "Give preference to those which either attach directly to the vehicle floor, or to the vehicle seat belt, not to the seat back". This, again provides the same two hazards, the crushing, forward-moving seat back, and the linear forces compressing the spine.

We wish to emphasize that these two hazards are definitely and completely eliminated in the belt which we make, and which is partially indicated in your drawing, but without explanation or comment.

Our harness is not attached directly to the car floor. It is attached directly to the seat back, which in turn is securely attached to the car floor. This holds the seat back securely in its place in a crash, and it also eliminates the linear spinal pressure. The child harness is free to slide up and down along the anchor strap which extends vertically at the front of the seat back. This provides two important safety features. First, it assures that the impact force will always be restrained from a point horizontal to the position of the body at the instant of impact, whether this position is standing, sitting or lying down. Not only will this restraining force be applied directly linear to the impact force but the construction and attachments of our harness assures that such restraint force will be applied to the front of the child and never at the side or rear which might cause neck or spinal injury.

The other, and very important safety feature of our harness is the complete and instantaneous freedom of movement of the child. A child of 2 or 3 years cannot be forcibly restricted to a single sitting position during a long ride without venement and justifiable protest, and consequent distraction of the driver's attention.

This brings us to the last of your statements on that page, viz. "Caution: Parents are warned not to allow a child to stand on the front seat of the vehicle when utilizing a harness restraint, or this may happen". The accompanying drawing indicates a typical whiplash injury situation. To eliminate this hazard, and still provide the maximum safe freedom of movement, our harness includes a positive but adult-adjustible stop on the vertical anchorage strap, and our instructions include a positive warning to keep this stop adjusted to a point which will not permit the child to stand in any seat, front or rear, under any conditions which permits his head to extend to a point higher than the top of the seat back.

We very strongly feel that, in your sincere efforts to educate the public and save the lives of children, you should see to it that these erroneous implications are promptly corrected and that such corrections be given as wide publicity as the original pamphlet.

We shall be awaiting your reply with interest.

C. W. Rose Chairman of the Board