Interpretation ID: 2874o
President
Liability Research, Inc.
4448 Via Esperanza
Santa Barbara, CA 93110
Dear Mr. Friedman:
This is a response to your letter dated November 17, 1987, asking whether two child restraint systems you have designed comply with certain requirements of Federal motor vehicle safety standard 213, Child Restraint Systems. You call one system "Cradle Safe," and describe it as an inclined, rear-facing, deformable, vinyl-covered woodfiber board carrier designed to restrain new-born infants from 4.5 to 14 lbs. The second system you call "Premie Cradle," and describe it as a recumbent, rear-facing, deformable, vinyl-covered woodfiber board carrier designed for premature infants from 4 to 6 lbs.
Your letter assesses the performance attributes of these systems as follows:
"In an accident the baby is oriented and cushioned to avoid injury and ejection by a deformable, energy absorbing 'bed' and 'shell' without harnessing the infant.
The bed and its crushable extensions (wings) cause the infant to rotate and take acceleration forces through its back and limit those applied to the head. After rotation, the infant is cushioned by the collapsing bed."
You state your belief that both systems comply with applicable provisions of Standard 213, but ask for our comment because "the designs are innovative and make the applicability and interpretation of certain paragraphs of the standard not entirely obvious." To help the agency better understand your products and the methods you used to test performance, you requested that agency staff meet with you, and your colleague, Mr. David Shinn.
On April 12, 1988, a meeting was held with you, Mr. Shinn, and agency staff from the following offices: Chief Counsel, Enforcement, Plans and Policy, Research and Development, Rulemaking, and Traffic Safety Programs. At that meeting, you and Mr. Shinn presented a video-film showing two sled-tests of your cradle-safe restraint system, one with a NHTSA-specified, 17 pound dummy, and one with an EEC eight pound dummy. In the video film, your child restraint system broke apart in the 30 mph test with the 17 pound dummy, but appeared to maintain its structural integrity when tested with the eight pound dummy. You did not show a sled-test with your "Premie Cradle" product.
By a letter dated June 8, 1988, you informed this agency that you had performed tests of a "modified" Cradle-Safe restraint system, and that this system will contain the NHTSA-specified 17 pound dummy in simulated barrier-impact testing under Standard 213. You state further that a restraint system you call "One-ride" also will contain a 17 pound dummy in Standard 213 testing. (You did not address the "One-ride" restraint in your November 17, 1987, correspondence, nor did you present it during the April 12, 1988 meeting.) Your June 8 letter also references a letter of July 22, 1987, addressed to Mr. Val Radovich of this agency; a June 3, 1988 video tape showing a simulated barrier impact test of your Cradle-Safe seat with a 17 pound dummy; and submissions of patent documents in support of a patent application for your products.
As NHTSA staff understood from your November 17, 1987 letter, and the April 12, 1988 meeting, your principal question was whether you could test a Standard 213 child restraint system with an eight or 14 pound dummy (rather than the specified 17 pound dummy), if you intended to label the restraint as appropriate for children from 4.5 to 10 pounds. You briefly addressed the other matters raised in your November 17, letter, clarifying a reference to an "unspecified belt provided for use outside the vehicle and not required in (Standard 213) testing." You explained that the "belt" to which you refer is a two-piece, cloth wrap that anchors at either side of the restraint, and fastens over the child with a velcro attachment.
I shall respond to your comments in the order that you present them in your letter, also discussing new matters raised in the meeting, in the June 8, 1988 letter, and in your other submissions where appropriate. I will not discuss the patent materials because they are not relevant to a determination of whether your restraint systems comply with Standard 213. In responding to your comments, I assume that we are discussing only those child restraint systems designed for children weighing less than 20 pounds (infant restraints).
Your First Comment. Paragraph 5.1.1.a dealing with Child Restraint System Integrity specifies "no complete...and no partial separation" of surfaces. Our design is deformable and involves materials of 1/4" thickness which in deforming, tear slightly. However when torn these materials are not lacerating and not likely to come into contact with the infant.
Response. Paragraph S5.1.1(a) states that when a child restraint is tested as specified in the Standard, the system shall:
Exhibit no complete separation of any load bearing structural element and no partial separation exposing either surfaces with a radius of less than 1/4 inch or surfaces with protrusions greater than 3/8 inch above the immediate adjacent surrounding contactable surface of any structural element of the system.
If the system failure you describe as tearing of materials at the system surface does not result in a failure of the load-bearing structure of the system, then paragraph S5.1.1(a) is inapplicable. In 1978, NHTSA proposed adding this language to 213 as one of a number of amendments to the Standard that would upgrade performance requirements, improve performance criteria, and require dynamic testing of child restraint systems using anthropomorphic test dummies. (43 FR 21470, 21473, May 18, 1978.) In the preamble of that document, we stated that our objectives in promulgating the system integrity requirements were to prevent a child's excessive excursion or ejection from the system, and to ensure that the system does not fracture or separate in such a way as to harm the child. (43 FR 21470, 21473.)
To accomplish this objective, Standard 213 requires that in dynamic testing, any load-bearing, structural element of a child restraint system must not separate completely; and that any partial separation must not expose surfaces with sharp edges that may contact the child. Id. Your letter states that some materials at the surface of your system may tear during an impact. In promulgating S5.1.1(a), the agency intended to minimize dangers resulting from failures in the structural integrity of the system, rather than failures in the materials. The agency did not intend to preclude a manufacturer from designing some deformation into a child restraint system to improve the system's energy absorption performance.
Your Second Comment. Paragraph 5.2.3.2.b The system surface in contact with the infant's head shall be covered with slow recovery, energy absorbing material. Although our system surfaces are not covered, they are fabricated out of such material. The system surface in contact with the infants head (the bed) is 3/16" woodfiber separated by air from a similar material in the shell. The system complies with the requirement and when dynamically tested exhibits deformation much better than a 25% compression-deflection, but there is no appropriate ASTM Test Standard such as for open or closed cell foam.
Response. As I read your comment, you raise three issues which I shall address separately. The first is whether the material from which you fabricate your system can meet the S5.2.3.2(b) requirement that a child restraint system must be "covered" with slow recovery, energy absorbing material. The agency's long-standing position is that a given type of surface material is an acceptable "covering" if it is a flexible material that would meet the thickness and performance requirements for energy-absorbing padding set out in paragraphs (a) and (b) of S5.2.3.2. The surface needn't have a separate layer of energy-absorbing padding.
The second issue is whether 3/16 inch woodfiber is a sufficient thickness for a system surface. This thickness would not comply with S5.2.3.2(b) of Standard 213. That subparagraph requires thicknesses of at least 1/2 or 3/4 inch, depending on the material's compression-deflection performance as measured in the static testing specified in S6.3 of Standard 213.
You assert that the 3/16 inch thickness material used in your systems exceeds a 25% compression-deflection measurement in dynamic testing. In the preamble to the final rule amending Standard 213, NHTSA responded to commenters who suggested that specifying a minimum thickness for the infant restraint surface was design-restrictive. (44 FR 72131, 72135, December 13, 1979.) We explained in that document that we set these minimum thickness requirements because there was no available test device to measure the energy absorption properties of either the surface or underlying structure of an infant restraint in dynamic testing. Consequently, the agency specified "long-established static tests" of the surface material, and established minimum thickness requirements based on the results of those static tests. Therefore, a compression-deflection measurement derived from dynamic testing is not an acceptable test of compliance with paragraph S5.2.3.2.
The third issue is whether the compression-deflection measurement for this system must be derived from tests under one of the ASTM standards in S6.3, even though none of the ASTM titles expressly states that the test is for woodfiber, and all three procedures are for static tests. Paragraph S5.2.3.2(b) requires that when one tests the energy absorption properties of child restraint materials, those tests must be conducted under one of three ASTM static test procedures set out in paragraph S6.3 of Standard 213.
Your restraint systems are made of woodfiber. Woodfiber - or any material that meets the Standard's requirements - can be an acceptable substance out of which to fabricate a child restraint. As NHTSA stated in the final rule preamble cited earlier, the agency wishes to allow restraint manufacturers to use a wide range of materials, provided that the material exhibits acceptable energy absorption properties. You may use any ASTM title specified in paragraph S6.3 to test your surface material, and the material is acceptable if it displays the required energy absorption properties when tested under one of those titles.
Your Third Comment. Paragraph 5.4.3.1 "Each belt that is part of a child restraint system and that is designed to restrain a child using the system..." is interpreted to mean that a soft unspecified belt provided for use outside the vehicle and not required in testing, need not conform to this paragraph.
Response. As you explained in the April 12, meeting, the "belt" to which you refer is the cloth device described in the beginning of this letter. By its express terms, paragraph S5.4.3.1 is inapplicable to belts that are (1) not part of the child restraint system and (2) not designed to restrain a child using the system. On the other hand, I note that in the June 8, video tape, the narrative refers to a belt within the Cradle-Safe system as a belt for restraining the child. If you do intend any belt in the system to be used for restraining the child, then various provisions of paragraph S5.4.3, Belt Restraint, will apply, depending on the design configuration of the belt assembly.
In the preamble to the May 1978 proposal cited earlier in this letter, the agency expressed its continuing concern that child restraint system designs minimize the prospect of system misuse. (43 FR 21470, 21471.) If there are belts in any of your child restraint systems that you do not intend as restraints for the child, then I hope you will consider whether these additional belts unreasonably increase the risk that some users will mistake the additional belt assembly as a Standard 213 belt intended for use in restraining a child.
Your Fourth Comment. Paragraph 6. This paragraph requires the CRADLE SAFE to be tested with a paragraph 7 dummy (17 lb.) for which it was not designed and which cannot be physically accommodated. We would prefer to use available 7.8 lb. and/or 14 lb. non-specified dummies. The PREMIE CRADLE falls in the car bed "travel crib" category and does not require dynamic testing.
Response. Paragraph S7.1 of Standard 213 requires testing an infant restraint system with the 6-month-old dummy specified in 49 CFR 572.25. (An infant restraint system is one that is recommended "for use by children in a weight range that includes children weighing not more than 20 pounds.") That test device is 17.4 pounds. Because your child safety system meets the definition of infant restraint, it must be capable of meeting Standard 213 performance requirements when tested with the specified 17.4 pound dummy. If an infant restraint can not accommodate this test device, then it can not be certified as complying with Standard 213. I understand from your June 8, 1988, letter that the Cradle-Safe and One-Ride systems will accommodate the specified 17.4 pound dummy in Standard 213 testing. Further, your restraint systems must meet head excursions limits with the 17.4 pound dummy under paragraph S5.1.3.2, Rear-facing Child Restraint Systems.
The dummy specified in Part 572 is based on a simple design that represents a 6-month-old infant in dimensional, mass distribution, and dynamic response characteristics. NHTSA chose to use this test dummy after conducting extensive testing and evaluation of the dummy's responses. The testing, conducted by NHTSA and the Federal Aviation Administration (FAA), showed that the specified dummy provided a consistent and repeatable measure of the structural integrity and confinement properties of a child restraint system, and was superior to a previous test version. (43 FR 21490, May 18, 1978; 44 FR 76527, December 27, 1979.) Before we can sanction use of another device to test an infant restraint system, the agency would have to determine that the dummy is a reliable surrogate for measuring a system's performance in an actual crash. NHTSA can not now make that statement with respect to any unspecified dummy, instrumented or non-instrumented. The agency can make this kind of finding only through a rulemaking process.
Further, contrary to what you believe, infant car beds are subject to dynamic testing to ensure that the test dummy stays within the confines of the restraint system during impact. (Standard 213, S6.1.2.3.3.)
While you believe you have identified some potential problems with Standard 213, I am sure that you can appreciate the need to follow established procedures when considering any change to a safety standard. Following established practices helps ensure that child restraint systems which comply with Federal standards continue to offer satisfactory crash protection for children. The agency has scheduled two public meetings this summer in order to explore the need for changes to Standard 213. I enclose a copy of the notice announcing these meetings, and invite you to participate in the forum.
Based on the information you provided, it appears that you would have to modify your systems, or the agency would have to amend Standard 213 in order for you to be able to certify your child restraint system as satisfying all the applicable requirements of that Standard. Title 49 CFR Part 552, Petitions for Rulemaking, Defect, and Noncompliance Orders (copy enclosed) sets out a procedure for petitioning the agency to amend a safety standard, and you have a right to file such a petition. If NHTSA grants your petition, the agency would follow its normal rulemaking procedures to amend Standard 213.
If you have some further questions or need further information on this subject, please contact Joan Tilghman of my staff at our address, or telephone (202) 366-2992.
Sincerely,
Erika Z. Jones Chief Counsel
Enclosures ref:213 d:7/8/88