Dear [                    ]:


This responds to a January 7, 2020, letter from [               ] that [      ] emailed to us on [   ]. We apologize that we were unaware of the January 7 letter prior to your contacting us. The letter asks about Federal Motor Vehicle Safety Standard No. 213 (FMVSS 213), “Child restraint systems,” as applied to a child restraint system (CRS) consisting of a “shell” 1 and a separate, detachable base. [  ] asks us to confirm that the shell and base “need only meet the requirements of FMVSS 213 when evaluated together as a system.” As explained below, we disagree with this view.


[      ] asks about a CRS design concept it calls the “Z Project.” The Z Project child restraint system has the following three components: (1) a rear-facing-only infant car seat shell (the “Z Infant Shell”); (2) a convertible2 shell that is used both rear-facing and forward-facing (the “Z Convertible Shell”); and (3) a detachable base with permanently attached components for securing it to the vehicle with either the lower anchors of the LATCH3 system or a vehicle’s Type 1 or 2 belt system (the “Z Base”).4


[      ] would like to offer the Z Project for sale in the United States in the following variations, which it calls “Sales Variations”: (1) a Z Infant Shell and Z Base, packaged together at retail and sold as a system; (2) a Z Base sold separately at retail; (3) a Z Convertible Shell and Z Base, packaged together at retail and sold as a system; and (4) the Z Convertible Shell purchased separately upon verification that the consumer is in possession of a Z Base.




1 Based on your letter and submissions, the shell consists of a molded plastic frame structure and the padding, padding cover, harness belt straps, belt buckles and labeling of a conventional child restraint.

2 As defined on NHTSA’s website, a “convertible” CRS is a type of CRS that “converts from rear-facing for babies and smaller children to forward-facing for older and larger children.” https://www.nhtsa.gov/car-seats-and-booster- seats/car-seat-glossary. [Footnote added.]

3 “LATCH” refers to the child restraint anchorage system that FMVSS 225, “Child restraint anchorage systems,” requires to be installed in motor vehicles. Industry and advocates have developed the term “LATCH” to refer to Standard 225’s child restraint anchorage system.

4 According to [   ] letter: “The Z Infant Shell installed with the Z Base will accommodate children from 4 to 35 lbs. The Z Convertible Shell installed with the Z Base will accommodate children from 4 to 50 lbs. rear-facing and 22 to 65 lbs. forward-facing.”



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[     ] asks about the permissibility of Sales Variations 3 and 4 where the “Shell” of the convertible child restraint is a separate component from the base. According to [    ], the Shell and Base are separate parts and may not even be sold together. As explained below, we believe Sales Variations 3 and 4 are not permitted by Standard 213.


Sales Variations 3 and 4

Standard 213 (section S4) defines a “child restraint system” as “any device, except Type I or Type II seat belts, designed for use in a motor vehicle or aircraft to restrain, seat, or position children who weigh 36 kilograms (kg) (80 lb) or less.” Standard 213 requires “child restraint systems” to meet performance requirements to minimize the risk of injury in a crash and ease-of- use requirements to increase the likelihood of consumers correctly using and installing CRSs.

Any device meeting the standard’s definition of a “child restraint system” must be certified to Standard 213’s requirements.


Because the Z Convertible Shell (without the Z Base) consists of a molded frame structure that also has the padding, padding cover, harness belt straps, belt buckles and labeling of a conventional convertible CRS, the Z Convertible Shell (without the Z Base) is a device designed to “restrain, seat or position children who weigh 36 kg (80 lb) or less” in motor vehicles. Based on this information, we believe the Z Convertible Shell meets the definition of a “child restraint system” and is a child restraint system in and of itself, without the Z Base. As a CRS, the Z Convertible Shell must meet the applicable requirements of Standard 213 standing alone, without use of a separate part or accessory like the Z Base.


Apparent Non-Compliances

It does not appear that the Z Convertible Shell would meet all applicable requirements of Standard 213. We discuss two apparent non-compliances below.


a.    S5.3.2 of Standard 213 requires each convertible CRS to meet the requirements of the standard when installed solely by each of the following means: (1) a Type 1 seat belt assembly (lap belt);5 (2) a Type 1 seat belt assembly plus a tether anchorage, if needed; and (3) the child restraint anchorage system specified by FMVSS No. 225 (LATCH system).






5 NHTSA has proposed to amend Standard 213 to refer instead to a Type II belt (lap-shoulder belt). Notice of proposed rulemaking, 85 FR 69388, November 2, 2020. This proposal does not affect our determination here that the Z Convertible Shell must have a means to attach to the vehicle seat by way of the belt system.



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As [       ] describes the Z Convertible Shell (p. 3 of your letter), “there is no belt path for vehicle belt installation and there are no lower anchor LATCH attachment mechanisms.” As such, it appears the Z Convertible Shell would not meet S5.3.2 as it has no means of attaching to a vehicle by a seat belt or by the child restraint anchorage system. The Z Convertible Shell depends on the Z Base for vehicle attachment, but the Z Base is wholly separate from the Z Convertible Shell. A CRS that cannot be installed solely by a belt and by a child restraint anchorage system will not meet S5.3.2.6


[    ] believes that Standard 213’s requirements apply to the “entire system” and not to the Z Convertible Shell alone. This view does not accord with the language of the standard. The Z Convertible Shell alone restrains, seats or positions children weighing 36 kg (80 lb) or less in motor vehicles and thus is a “child restraint system” in and of itself. It must meet S5.3.2 solely by the belt and LATCH system without having to depend on an added separate part.


[     ] view is also at odds with the purposes of S5.3.2, which is to standardize the means of vehicle attachment and increase the likelihood of a correct and safe installation. The standard requires CRSs to provide at least a minimum level of safety without use of additional parts, to ensure that the restraint will provide an adequate level of protection in the event the additional parts are not used.7 A CRS design whose minimal crash protection is dependent on a consumer’s using supplemental parts is contrary to this purpose and is not permitted unless explicitly provided for by the standard.


b.    S5.9(a) of Standard 213 requires each child restraint system to have permanently attached components that enable the CRS to be securely fastened to the lower anchorages of a child restraint anchorage system.8 The Z Convertible Shell attaches to the Z Base and the Z base is equipped with said components, but the Z Base is not a permanent part of the Z Convertible Shell. S5.9(a) states: “The components must be attached by use of a tool, such as a screwdriver.” The Z Convertible Shell does not have the child restraint anchorage system components attached to it by use of a tool like a screwdriver and so does not meet the requirements of S5.9(a).


One of NHTSA’s goals in establishing a child restraint anchorage system is to increase correct CRS use by ensuring that child restraint systems are convenient to install and use and are accepted by consumers.9 NHTSA adopted the “permanently attached” requirement in S5.9(a) to better ensure that the components on a CRS that attach to the child restraint anchorage system will be present and available for use by consumers through the life of the CRS.10 This is especially important with regard to child restraints, as it is common for child restraint systems to be handed down to others or otherwise re-used.



6 The Z Convertible Shell would have to meet other performance requirements of FMVSS 213 without use of the Z Base. For instance, the Z Convertible Shell would have to meet the head and knee excursion requirements without the use of a tether strap.

7 Mercedes-Benz letter, https://isearch.nhtsa.gov/files/17513mer.b-i.htm. “Add-on, nonpermanent components can be lost or misplaced and may not be accessible when the restraint has to be used.” This interpretation concerns an “impact shield” that was not “formed as a unit” with the built-in CRS.

8 FMVSS 213 S5.9(a) inadvertently refers to a child restraint “anchorage” system instead of a “child restraint

system.” As indicated by the context of S5.9(a) and by the final rule adopting S5.9(a) (64 FR 10786, 10816; March 5, 1999), reference to “anchorage” is incorrect. NHTSA plans to correct the word soon.

9 LATCH final rule, 64 FR at 10797, col. 2.



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This interpretation is consistent with an April 26, 2007, interpretation addressing whether a CRS could be designed so that it attached to the child restraint anchorage system using a part that was called an “ISOFIX platform.”11 The ISOFIX platform appears similar to the Z Base: it alone had the child restraint anchorage system attachment and the CRS would attach to the ISOFIX platform. NHTSA stated the CRS design would not meet the requirements of Standard 213 because, although the CRS was designed to attach to the ISOFIX platform, FMVSS 213 requires the components attaching to the child restraint anchorage system to be permanently attached to the CRS. The agency did not regard the CRS and the ISOFIX platform as together comprising the “child restraint system.” Accordingly, NHTSA determined that the sale or importation of the CRS into the U.S. would be prohibited.


[    ] believes that the aforementioned Mercedes-Benz (MB) letter (footnote 7, supra) supports its view that NHTSA should apply FMVSS No. 213 to the Z Convertible Shell and the Z Base “together as a system.” The letter related to MB’s built-in12 booster seat that had a separate, non- integral “impact shield” and whether NHTSA would test the booster seat together with the impact shield. NHTSA said no, the booster seat must meet Standard 213’s requirements without use of the shield, because the impact shield was not part of the built-in CRS. We believe this outcome is consistent with our view in this letter that the Z Convertible Shell is a CRS unto itself and must meet Standard 213 without use of a separate part like the Z Base.


In answering MB, NHTSA also analyzed the applicability of the standard to various components of the MB system. [    ] focuses on the part of the MB letter that discusses whether the impact shield would be subject to the standard as an “add-on” child restraint system but, in doing so, [ ] appears to have misunderstood the context of and reasons for the agency’s statements. NHTSA’s statements related to its determination that the impact shield was not an add-on CRS due to the shield design and MB’s intention to sell the shield as part of the vehicle’s built-in system. NHTSA’s statement that the MB shield is “merely a component of a child restraint system and is not intended to be used separately from the other parts of the restraint system” was among those explaining why we concluded that the shield was not an add-on CRS that had to meet FMVSS 213 in its own right. The statements you quoted pertained to our decision that the MB shield was not an add-on CRS, and do not relate to how NHTSA would test an add-on system that had a separate part.


There are circumstances in which Standard 213 permits a child restraint to meet a requirement by way of a detachable base, but those situations are explicitly recognized in the standard and do not apply to your situation. For example, Standard 213 recognizes that some installation information may be on a detachable base (see, S5.5.3, which refers to the installation diagrams that must be visible when the CRS is installed).13 Another provision, discussed in a section below and one you ask about, relates to the last sentence of S5.9(a).





10 In the rulemaking establishing FMVSS 225, NHTSA considered the merits of allowing vehicle manufacturers the option of installing an anchorage system that some CRSs could use only through an adapter that interfaced between the CRS and the anchorage system. Commenters overwhelmingly opposed an adapter, believing that the adapter would likely be lost or misused by consumers. The agency agreed and decided to adopt an anchorage system that would be universal to all vehicles and all CRSs. The Z Convertible Shell is contrary to NHTSA’s purpose in developing FMVSS 225 and the related requirements of FMVSS 213 S5.3.2 and S5.9(a), as the Z Base acts as an adapter that must be used for the CRS to attach to the anchorage system.

11 Gazza letter, https://isearch.nhtsa.gov/files/005431rls.htm.

12 FMVSS No. 213 (S4) defines a “built-in child restraint system” as “a child restraint system that is designed to be an integral part of and permanently installed in a motor vehicle.” An “add-on” system is a portable child restraint system (S4).



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Your Question about the Last Sentence of S5.9(a)

The last sentence of S5.9(a) states: “In the case of rear-facing child restraints with detachable bases, only the base is required to have the components [that are permanently attached to the CRS that enable the restraint to be securely fastened to the lower anchorages of the child restraint anchorage system].” You believe this provision would permit the Z Convertible Shell to have the anchorage system components attached only to the detachable base (the Z Base).


Your understanding is incorrect. The provision only applies to rear-facing child restraints and does not apply to a convertible child restraint system like the Z Convertible Shell, because a convertible CRS is also a forward-facing child restraint system. If a child restraint could also be used forward-facing, the provision does not apply. NHTSA drafted the last sentence of S5.9(a) envisioning the provision as applying to “infant-only restraints with detachable bases.”14 The provision was adopted out of a concern at the time about the cost impacts of the rule on infant carriers (i.e., CRSs that are used rear-facing only).


Sales Variation 1

Please note that it appears the Z Infant Shell described in Sales Variation 1 must have a belt path for a vehicle belt installation (S5.3.2). The Z Infant Shell is a “child restraint system” under FMVSS No. 213 and, unless excepted by the standard,15 must meet the requirements of the standard standing alone without use of a separate part like the Z base. We cannot tell from materials whether there is a belt path on the Z Infant Shell itself. Please ensure that the Z Infant Shell in Sales Variation 1 has the required means of attaching by way of a vehicle seat belt assembly without the detachable base (Z base), as required by FMVSS No. 213 S5.3.2.


If you have other questions, please contact Deirdre Fujita of my staff at (202) 366-2992.




   Digitally signed by ANN

                     ELIZABETH CARLSON

Date: 2022.05.31

11:46:31 -04'00'

Ann Carlson

Chief Counsel


Dated: 5/31/22

Ref: FMVSS No. 213




13 In a January 16, 2003, letter (Meyer letter, https://isearch.nhtsa.gov/files/00070cmc.html), the agency addressed whether a CRS with a detachable base must have information labeled on the base if the seating portion of the CRS was already properly labeled. The agency said no, “a detachable base is part of a child restraint system” so “[a]s

long as the labeling requirements are met by the system as a whole, the base is not required to be labeled.” We do not give weight to this letter as it was narrowly focused on labeling, did not analyze S4’s CRS definition, S5.3.2, and S5.9(a), and was overtaken by the April 26, 2007 Gazza letter, supra, that found an ISOFIX platform not to be part of the child restraint. To the extent the Meyer letter is inconsistent with this and the Gazza letter, we consider the Meyer letter superseded.

14 Final rule preamble, 64 FR at 10806 (col.3). The discussion of the provision begins with: “Several commenters addressed the requirements that would apply to infant-only restraints with detachable bases.”

15 E.g., as noted above, the last sentence of S5.9(a) permits the rear-facing child restraint to use the Z Base to attach to the child restraint anchorage system, and S5.5.3 provides for some labeling to be on a detachable base.