nht81-3.38 | NHTSA

DATE: 11/12/81

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Cosco

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your letter concerning the application of Standard No. 213, Child Restraint Systems, to a booster seat that uses a vehicle lap belt or lap/shoulder belt to restraint a child weighing 20 or more pounds. The following discussion answers your questions concerning the application of specific sections of the standard to a booster seat.

Section 4 of the standard defines a "child restraint system" as "any device, except Type I or Type II seat belts, designed for use in a motor vehicle to restrain, seat, or position children who weigh not more than 50 pounds." Since the booster seat you described would be used to seat a child weighing less than 50 pounds in a vehicle, it is a child restraint system and thus must meet the requirements of the standard. The vehicle lap belt (Type I belt) or lap/shoulder belt (Type II belt) used with the system are specifically excluded by the definition of child restraint system and thus are not covered by the requirements of the standard.

You said that the booster seat would have no sides, back or fixed or movable surface directly in front of the child and asked how the standard would apply to such a design. The standard does not require a child restraint to have a back, sides or fixed or movable surface in front of the child. If such surfaces are provided, however, they must comply with the applicable requirements of sections 5.2.2, 5.2.3, and 5.2.4.

Each child restraint is required to meet the minimum head support surface requirements of S5.2.1. Section 5.2.1.2, however, exempts forward-facing child restraint from the minimum head support surface requirement if, "the target point on either side of the dummy's head is below a horizontal plane tangent to the top of the standard seat assembly when the dummy is positioned in the system and the system is installed on the assembly in accordance with S6.1.2." Thus, unless your design is within the exception of S5.2.1.2, it would have to comply with the minimum head support requirements of S5.2.1.1. Any head support surface would also have to comply with the applicable requirements of S5.2.3. and S5.2.4.

You asked about the application of S5.4.3.2 to a booster seat. Section 5.4.3.2 provides that:

Each belt that is a part of a child restraint system and that is designed to restrain a child using the system and to attach the system to the vehicle shall, when tested in accordance with S6.1, impose no loads on the child that result from the mass of the system or the mass of the seat back of the standard seat assembly specified in S7.3. (Emphasis added.)

As previously mentioned, the definition of a "child restraint system" specifically excludes Type I or Type II seat belts from the coverage of the standard. Thus, under that definition and the language emphasized above, the requirements of S5.4.3.2 do not apply to the lap and lap/shoulder belts used with a child restraint system. The agency, however, is concerned that when a vehicle lap belt is used with a child restraint system to restrain a child that the lap belt be positioned so that it does not apply impact loads to the abdomen of the child, the area most vulnerable to the forces imposed by the belt. Instead, the vehicle lap belt should be held in place by the child restraint so that it passes over the pelvis and thighs of a child, areas of the body best able to withstand the forces imposed by the vehicle belt. Based on the drawing of your restraint, we are concerned that the vehicle lap belt may not be properly positioned and securely held by the restraint. Instead, the lap belt may allow submarining and may apply impact loads to the abdomen. The agency is also concerned that the lap belt should be properly positioned and securely held so that no substantial inertial loads of the booster seat are applied to the child.

You stated that the booster seat would not have a harness system when it is used at a vehicle seating position equipped with a lap/shoulder belt. The standard does not require the use of a harness in a child restraint system. Section 5.4.3.3 of the standard provides, in part, that "each child restraint system . . . that has belts designed to restrain the child" must comply with the specific requirements of S5.4.3.3. (Emphasis added.) Thus, the specific requirements of S5.4.3.3 on harness systems only applies if a manufacturer provides belts as a part of the system.

Finally, you said that the booster seat would be sold with an auxiliary tethered shoulder harness. The harness would attach to the vehicle lap belt when the booster seat is used at a vehicle seating position that has no lap/shoulder belt. The harness would not have a crotch strap. As discussed previously, section 5.4.3.3 of the standard specifies the requirements that a child restraint system which provides a belt system must meet. S5.4.3.3(c) provides:

i) a crotch strap connectable to the lap belt or other device used to restrain the lower torso, or

ii) a fixed or movable surface that complies with S5.2.2.1(c).

The purpose of subsection (c) is to require a belt or surface design that will prevent the child from submarining under the lap belt (i.e., sliding down and forward under the belt). Thus, if a crotch belt is not provided, the surface of the restraint must be designed to prevent submarining and comply with S5.2.2.1(c). For example, the seating surface of the restraint could be designed to prevent submarining.

If you have any further questions, please let me know.

SINCERELY,

COSCO

Frank Berndt, Chief Counsel U.S. Dept. of Transportation National Highway Traffic Safety Administration July 27, 1981

Dear Mr. Berndt:

We are in the process of evaluating various new concepts for future child restraints we may produce. In this evaluation, we are uncertain what will or will not be allowed under the 213-80 juvenile car seat standard on designs that have a minimal "booster" seat and rely on the automobile adult lap belt or the auto adult lap/shoulder belt as a direct means of restraining the child.

If we had a design that was specified to be used only by children over 20 lbs., that had a firm seating platform with no sides or back, that by its design properly positioned the auto's three (3) point adult lap/shoulder belt for this age of child to provide adequate protection during dynamic testing, would such a design be allowed by the 213-80 juvenile car seat standard? It should be noted that the auto belts would be in direct contact with the child; there would be no other harness belts when used in an auto seat that provides a lap/shoulder belt; there would be no crotch strap at any time, but there would be an auxiliary tethered shoulder harness that would attach to the auto lap belt for use where no automobile lap/shoulder belt is provided. Finally, there would be no fixed or movable surface directly forward of the child. A drawing representing this concept is attached.

There are several sections of the standard that need interpreting on how they relate to such a design. They include Sections S5.4.3.2. through to Section S5.5 and others.

Would you please give us your official interpretation on whether this proposed design would comply with the 213-80 standard? We hope you will be able to give these questions your immediate attention.

Roy Knoedler Senior Industrial Designer

ENC.

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Interpretation ID: nht81-3.38