Three forward-facing CRS models (Evenflo Triumph,\82\ Evenflo Titan and
Evenflo Tribute) and three rear-facing CRS models (Evenflo Tribute,
Safety 1st Alpha Omega and Graco My Ride 65) were tested using the Q3s
dummy on the final SISA to compare to the results from corresponding
sled tests conducted on the proposed SISA. Paired comparison analyses
(see Table 11) show that HIC15 and chest deflection results on the
proposed and final SISA were not significantly different (p>0.05).
These data indicate that changes to the SISA between the NPRM and final
rule did not affect test results from tests of the CRSs.
---------------------------------------------------------------------------

    \82\ The Evenflo Triumph was produced in 2009 which ensured this
model had not been modified to improve side impact in response to
the 2014 NPRM. The agency also tested a more recently produced model
which had very similar performance.

                 Table 11--Paired Comparison T-Test Results of Tests Conducted Using the Final SISA Configuration and the Proposed SISA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Final rule SISA configuration                                NPRM SISA configuration
                                     -------------------------------------------------------------------------------------------------------------------
 Dummy, configuration and restraint                                                    Chest                                                     Chest
                type                   Test No.            CRS             HIC15    deflection   Test No.            CRS             HIC15    deflection
                                                                                [mm]                                                      [mm]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Q3s in Forward Facing (FF)                10274  Evenflo Triumph (2009)      498.8        11.4       7561  Evenflo Triumph             463.8        14.6
 Convertible Installed with CRAS.                                                                           Advantage DLX.
                                                                                8252  Evenflo Triumph             445.8        16.1
                                                                                Advantage DLX.
                                                                                8254  Evenflo Triumph             468.7        13.5
                                                                                Advantage DLX.
                                          10276  Evenflo Titan.........     1029.3        28.3       7557  Evenflo Titan.........      846.5        20.6
                                          10101  Evenflo Tribute.......      760.0        20.9       7547  Evenflo Tribute.......      788.0        20.2
                                                 T.Test................      0.192       0.897  .........  ......................  .........  ..........
Q3s in Rear Facing (RF) Convertible       10282  Evenflo Tribute.......      611.5        23.4       7554  Evenflo Tribute.......      763.0        22.4
 Installed with lower anchors only
 (LA only).
                                          10283  Safety 1st Alpha Omega      396.4        26.0       7553  Safety 1st Alpha Omega      407.0        25.6
                                          10284  Graco My Ride 65......      778.3        22.3       8260  Graco My Ride 65......      751.0        25.0
                                                                                8264  Graco My Ride 65......      681.0        31.0
                                                 T.Test................      0.869       0.341  .........  ......................  .........  ..........
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The second part of the testing was to assess the performance of
more recently produced child restraint systems to the requirements of
then-pending FMVSS No. 213a. NHTSA conducted 18 tests of 17 CRS models
on the final SISA configuration. The 17 models represented 9 different
types of child restraints, including infant, convertible

and combination CRSs. NHTSA selected CRSs that had a variety of self-
described (advertised) side impact protection features.
    The data from the 2017 test program indicated that child restraint
system designs had changed since the publication of the NPRM in 2014.
Of the 17 models tested, one (1) model had no side impact protection
advertised, seven (7) models advertised that the product was side
impact-tested or had side impact protection, and nine (9) models self-
described the side impact technology used. Among the selected CRSs were
2 pairs of CRS models where one of the CRS had ``incremental'' improved
side impact protection, based on their product description, compared to
the other CRS. The Graco Nautilus and the Graco Nautilus Safety
Surround (discussed above this preamble) were very similar models but
the latter had a thicker head rest structure that was advertised as
providing extra protection. The Britax Boulevard and Britax Advocate
(also discussed above) were also CRSs that appeared to be similar, but
the Britax Boulevard only had two levels of side impact protection
while the Advocate had three levels of protection (according to the
advertising).
    NHTSA tested the child restraints with the Q3s 3-year-old child
dummy and the CRABI-12-month-old dummy. Forward-facing CRSs were
installed using the lower anchors of the child restraint anchorage
system required by FMVSS No. 225 and the tether anchorage, and rear-
facing CRSs were installed using the lower anchorages only. Tables 12
and 13 provide a test matrix of the CRS name, orientation, installation
method, dummy used and recorded injury measures.

     Table 12--Test Matrix and Summary Results of Tests With the Q3s ATD Using the Final SISA Configuration
----------------------------------------------------------------------------------------------------------------
                                                                                HIC15  [g]         Chest
                                                                                ----------------   deflection
      Database No.              CRS           Orientation        Installation                          [mm]
                                                                                IARV=570    ---------------
                                                                                IARV=23
----------------------------------------------------------------------------------------------------------------
10100..................  Chicco NextFit..  FF Convertible..  CRAS...............           582.0            18.7
10101..................  Evenflo Tribute.  FF Convertible..  CRAS...............           760.3            20.8
10102..................  Cosco Scenera     FF Convertible..  CRAS...............           979.8            26.8
                          Next.
10103..................  Maxi-Cosi Pria    FF Convertible..  CRAS...............           512.9            17.6
                          70.
10104..................  Evenflo Chase...  FF Combination..  CRAS...............           937.5            24.3
10105..................  Britax Boulevard  FF Convertible..  CRAS...............           521.7          * 7.08
10106..................  Britax Advocate.  FF Combination..  CRAS...............           665.3            18.3
10107..................  Safety 1st        FF Convertible..  CRAS...............           616.3            27.7
                          Advance SE Air+.
10108..................  Graco Nautilus    FF Combination..  CRAS...............           609.0            13.6
                          65.
10109..................  Graco Nautilus    FF Combination..  CRAS...............           838.5            17.9
                          Safety Surround.
10115..................  Cosco Scenera     RF Convertible..  LA Only............           677.7            26.2
                          Next.
10116..................  Graco Size4Me 65  RF Convertible..  LA Only............           778.5            23.5
10118..................  Evenflo Triumph.  RF Convertible..  LA Only............           487.8            12.2
10117..................  Baby Trend        RF Convertible..  LA Only............           963.7            25.8
                          PROtect.
----------------------------------------------------------------------------------------------------------------
Note: CRAS means the full child restraint anchorage system, LA Only means lower anchorages of the child
  restraint anchorage system, RF means rear-facing, and FF means forward-facing.
* Possible data anomaly.

    Results shown in Table 12 show that among forward-facing CRSs
tested with the Q3s dummy, 20 percent (2/10) had HIC15 values less than
or equal to the IARV of 570, and 70 percent (7/10) had chest deflection
less than or equal to the IARV of 23 mm. Among rear-facing CRSs tested
with the Q3s dummy, 25 percent (\1/4\) had HIC15 values less than or
equal to the IARV of 570 and 25 percent (\1/4\) had chest deflection
values less than or equal to the IARV of 23 mm.

     Table 13--Test Matrix and Summary Results of Tests With the CRABI 12-Month-Old ATD Using the Final SISA
                                                  Configuration
----------------------------------------------------------------------------------------------------------------
      TRC test No.              CRS              Orientation              Installation             Contact
----------------------------------------------------------------------------------------------------------------
10110..................  Britax B-Safe 35  RF Infant..............  LA Only................  No.
10112..................  Cybex Aton 2      RF Infant..............  LA Only................  No.
                          using
                          telescopic side
                          arm.
10111..................  Evenflo Embrace   RF Infant..............  LA Only................  No.
                          LX.
10114..................  Maxi-Cosi Mico    RF Infant..............  LA Only................  No.
                          AP.
----------------------------------------------------------------------------------------------------------------
Note: LA Only means lower anchorages of the child restraint anchorage system and RF means rear-facing.

    As shown in Table 13, rear-facing CRS (infant carriers) tested with
the 12-month-old CRABI dummy showed that 100 percent (4/4) met the
containment criteria.
General Observations
    The 2017 test results \83\ with the Q3s dummy show fewer child
restraints able to conform to the performance requirements of FMVSS No.
213a, compared to test results from earlier tests. In the 2014 tests
reported in the NPRM, among 12 CRS models in the forward-facing mode
tested with the Q3s dummy, 41 percent (5/12) had HIC15 values passing
the IARV and 75 percent (9/12) had chest deflection passing the IARV.
Additionally, 40 percent (2/5) of rear-facing CRSs tested with the Q3s
dummy had HIC15 and

chest deflection values passing their respective IARVs. Among rear-
facing CRSs (infant carriers) tested with the 12-month-old CRABI dummy,
91 percent met the containment criteria in the tests.
---------------------------------------------------------------------------

    \83\ Louden & Wietholter (2022). Available in the docket of this
final rule.
---------------------------------------------------------------------------

    It should be noted that for the fleet tests presented in the NPRM,
NHTSA selected the CRS models to obtain a representation of the market
at the time, with a variety of CRS manufacturers and models. For the
2017 testing done with the final SISA configuration, NHTSA selected
CRSs that had a variety of side impact protection features, but the
CRSs were not necessarily a representation of the market. The goal of
the second part of the tests using the final SISA configuration
presented in Tables 12 and 13 was to learn how the CRSs with advertised
improved side impact protection performed in the side impact test.
    To select the CRSs that would be tested for the final rule
evaluations, NHTSA examined CRS designs tested in 2011-2012 with
designs updated in 2016-2017. The comparisons of designs were only done
visually, i.e., NHTSA did not undertake tear-down analyses of the
underlying structure designs.
    In the test, the agency observed that some of the designs that were
not updated, or that were minimally updated, such as the Graco Classic
Ride 50,\84\ Evenflo Tribute, and Evenflo Chase, maintained the same
performance as in 2012 (see Table 5). In contrast, the performance
measures (HIC15, chest deflection, head contact) in other models that
had been redesigned since the NPRM were markedly different than in
their respective older versions. For example, the redesigned Britax
Advocate had higher HIC15 measures, and the Safety 1st Advance SE Air+
and Cosco Scenera had higher chest deflections (see Table 14) than
their respective prior versions. The redesigned Britax Advocate has a
different shell, a side structure with different shape and more
coverage (but has a similar adjustable head restraint as the older
version). The redesigned and prior versions of the Safety 1st and Cosco
models had differences in the side structures of the CRS at the head
and chest areas, and the newer versions appeared to be thicker in the
head and torso/pelvis area. The Graco Nautilus 65 2017 showed improved
chest deflections compared to the Graco Nautilus 2012, while the Graco
Nautilus Safety Surround 2017 had increased HIC15 compared to the Graco
Nautilus 2012.
---------------------------------------------------------------------------

    \84\ Also known as the Comfort Sport.

      Table 14--Comparison of the Performance of Forward-Facing and Rear-Facing CRS Models in Tests With the Proposed and Final SISA Configurations
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Chest
         Database No.                SISA configuration                CRS model                HIC15        deflection             Orientation
                                                                                [mm]
--------------------------------------------------------------------------------------------------------------------------------------------------------
7544.........................  NPRM.........................  Evenflo Chase..............             766            18.7  Forward Facing.
8253.........................  NPRM.........................                                          987            20.1
8255.........................  NPRM.........................                                          853            25.0
8257.........................  NPRM.........................                                          784            25.4
10104........................  Final........................                                          937            24.3
7547.........................  NPRM.........................  Evenflo Tribute............             788            20.2  Forward Facing.
10101........................  Final........................                                          760            20.9
8276.........................  NPRM.........................  Graco Classic Ride 50/Graco             742            19.3  Forward Facing.
                                                               Comfort Sport.
8278.........................  NPRM.........................                                          679            21.5
8280.........................  NPRM.........................                                          675            19.6
10020........................  Final........................                                          672            21.6
10021........................  Final........................                                          716            20.6
10022........................  Final........................                                          691            20.1
7545.........................  NPRM.........................  Britax Advocate............             365            19.5  Forward Facing.
10106........................  Final........................                                          665            18.3
7546.........................  NPRM.........................  Safety 1st Air Protect/                 624            16.5  Forward Facing.
                                                               Advance SE Air+.
10107........................  Final........................                                          616            27.7
8283.........................  NPRM.........................  Cosco Scenera/Scenera Next.             685            19.2  Rear Facing.
8285.........................  NPRM.........................                                          714            20.2
8287.........................  NPRM.........................                                          660            23.4
10115........................  Final........................                                          678            26.2
8277.........................  NPRM.........................  Graco Nautilus/Nautilus 65/             654            17.7  Forward Facing.
                                                               Nautilus Safety Surround.
8279.........................  NPRM.........................                                          597            19.5
8281.........................  NPRM.........................                                          625            17.0
10108........................  Final........................                                          609            13.6
10109........................  Final........................                                          839            17.9
7562.........................  NPRM.........................  Maxi Cosi Priori/Maxi Cosi              388            21.1  Forward Facing.
                                                               Pria 70.
10103........................  Final........................                                          512            17.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: Bold = Increased Value, Italic = Decreased Value.

    Based on this testing (Table 12 and Table 14) NHTSA believes that
some of the more recently tested CRS designs may have added unnecessary
bulk. Injury values are higher in some designs that had added mass
(thickness) \85\ than those without it. The 2017 testing indicates that
placement of coverage, materials, internal structures, shape of the
coverage and other factors must be purposefully engineered, as more is
not necessarily better.
---------------------------------------------------------------------------

    \85\ Table 10 of this final rule measured the width of the CRSs
with and without additional padding and documented the description
of the different side impact protection designs. Some CRSs were
simply visually inspected where they may have appeared to have
thicker structures.
---------------------------------------------------------------------------

    NHTSA had thought in the 2014 NPRM that CRSs with greater side
coverage performed better than CRSs with a less side coverage. Designs
meeting FMVSS No. 213a's performance requirements are feasible, but the
data

from the 2017 program show there are optimal ways to add structure and
padding, and ways that added bulk could have an adverse effect. The
test procedure adopted by this final rule will provide a means for CRS
developers to assess, in a meaningful way, the performance of their
designs and optimize the protection of children in side impacts.

d. The 40-lb Limit for Coverage of the Standard

    Consistent with the Safety Act and NHTSA's guiding principles for
this rulemaking, NHTSA proposed to apply the side impact test
requirements to CRSs designed to seat children in a weight range from
birth to 18.1 kg (0 to 40 lb). The Safety Act requires each FMVSS to be
appropriate for the particular type of motor vehicle equipment for
which it is prescribed.\86\ NHTSA determined the side protection
standard would be appropriate for child restraints for children in the
0 to 18.1 kg (40 lb) group \87\ because these children have a high rate
of child restraint use (less than 1-year-old = 97.5 percent and 1- to
3-years-old \88\ = 94.3 percent according to the 2019 National Survey
of the Use of Booster Seats (NSUBS) \89\). Their high use rate provides
a good opportunity for reducing injuries and fatalities through a side
impact regulation.\90\
---------------------------------------------------------------------------

    \86\ 49 U.S.C. 30111(b).
    \87\ This group encompasses children ages birth to about 4
years.
    \88\ Note that, in survey data, a child who is 1 day shy of his
or her 4th birthday is still considered a 3-year-old. Therefore,
survey data representing 1- to-3-year-old children include 3-year-
old children who are nearly 4-years-old. Also, the 40 lb weight
limit represents the weight of a 75th percentile 4-year-old child
and an average 5-year-old child.
    \89\ Enriquez, J. (2021, May). The 2019 National Survey of the
Use of Booster Seats (Report No. DOT HS 813 033). National Highway
Traffic Safety Administration. NSUBS is a probability-based
nationwide child restraint use survey conducted by NHTSA's National
Center for Statistics and Analysis (NCSA).
    \90\ Children between 4- and 12-years-old have lower child
restraint use (4- to 7-year-olds = 55 percent and 8- to 12-year-olds
= 6 percent). Data show that 43 percent of 4- to 7-year-old and 78
percent of 8- to 12-year-old children use seat belts.
---------------------------------------------------------------------------

    NHTSA also determined that focusing on the 0 to 18.1 kg (40 lb) (0-
to 4-years-old) age group is appropriate because countermeasures are
practicable for this age group. Real-world data show that head injuries
are the most common injuries in a side impact for 0- to 4-year-old
children. According to McCray,\91\ head injuries in children 1- to 3-
years-old are slightly higher than overall for children 0 to 12 year of
age. Using padding and/or larger side wings to keep the child's head
contained and protected enables forward- and rear-facing CRSs to meet
the requirements of this final rule without adding any additional
structures to the safety seats. The Q3s dummy is also representative of
children in the upper range of this age group and can be used to assess
the performance of child safety seat countermeasures in protecting
against unreasonable head impact.
---------------------------------------------------------------------------

    \91\ McCray, L., Scarboro, M., Brewer, J. ``Injuries to children
one to three years old in side impact crashes,'' 20th International
Conference on the Enhanced Safety of Vehicles, 2007. Paper Number
07-0186.
---------------------------------------------------------------------------

    NHTSA also explained in the NPRM that the FMVSS No. 213a side
impact test replicates a near-side crash as experienced by a child
under 18.1 kg (40 lb) in a safety seat. The agency's test results
indicate that an important factor in the near-side impact environment
is the position of the child's head with respect to the ``beltline''
(also referred to as the windowsill) \92\ of the vehicle door. When the
child's head is below the beltline--as likely with children weighing up
to 18.1 kg (40 lb) (0- to 4-year-old) in child restraints--protection
of the child is critically dependent on the child safety seat, as
negligible benefit is expected to be attained from the vehicle's side
curtain air bags. Older children restrained in CRSs typically sit high
enough so that the child's head is above the beltline and within the
area covered by the side curtain air bag.
---------------------------------------------------------------------------

    \92\ The beltline of a vehicle is a term used in vehicle design
and styling, referring to the nominally horizontal line below the
side glazing of a vehicle, which separates the glazing area from the
lower body. Passenger vehicles are required to provide head
protection in side impacts and ejection mitigation in rollovers,
pursuant to FMVSS No. 214 and FMVSS No. 226, ``Ejection
mitigation,'' respectively. The countermeasure provided to meet
FMVSS No. 226 in passenger vehicles, a side curtain air bag, must
meet performance requirements that, in effect, will necessitate
coverage of the side windows to the beltline of the vehicle.
---------------------------------------------------------------------------

    Finally, NHTSA emphasized that, due to the absence of an array of
side impact child test dummies, focusing this rulemaking on CRSs
designed for children in a weight range that includes weights up to
18.1 kg (40 lb) properly accords with 49 U.S.C. 30111(b)'s provision
that each FMVSS be appropriate for the types of motor vehicle equipment
for which it is prescribed. NHTSA determined that the Q3s dummy
(weighing 14.5 kg (32 lb)) is representative of young children weighing
under 18.1 kg (40 lb) and is appropriate as a test device for CRSs
recommended for children weighing up to 18.1 kg (40 lb). The dummy
would not be a suitable dummy to test the performance of CRSs in
protecting children weighing more than 18.1 kg (40 lb), as it is not
representative of children for whom the CRS is sold.
Comments Received
    NHTSA received diverse comments on the 40-lb applicability
threshold. Commenters generally agreed that the absence of a dummy
larger than the Q3s limited the agency's applying the side impact
standard to child restraints for children weighing more than 18.1 kg
(40 lb), but several commenters urged NHTSA to develop new test dummies
or use existing ones, such as frontal test dummies. No commenter
objected to NHTSA's requiring manufacturers of booster seats to limit
use of boosters to children weighing at least 18.1 kg (40 lb); six
commenters expressly supported the provision (IIHS, Dorel, Britax,
JPMA, UMTRI and Safekids). Advocates requested NHTSA provide more
support for its determination that children weighing more than 18.1 kg
(40 lb) may benefit from side curtain air bags.
    IIHS concurred with NHTSA's proposed threshold applying FMVSS No.
213a to CRSs for children weighing less than 18.1 kg (40 lb) for the
reasons given in the NPRM. IIHS provided data to support the view that
children weighing more than 18.1 kg (40 lb) in booster seats are seated
high enough to take advantage of the vehicle's side curtain air bags.
The commenter explained that data it obtained during its tests of
booster seat belt fit indicate that the center of gravity (CG) of a
typical 6-year-old child's head is 600-650 millimeters (mm) above the
vehicle seat when seated in a booster, which is above the windowsill
(beltline) of 500 mm discussed in the NPRM.\93\ IIHS found that on
average, the seated height of the 6-year-old dummy in a booster seat is
within a few centimeters of the seated height of the 5th percentile
adult female dummy used in the rear seat of IIHS's dynamic side impact
test. IIHS stated that in the most recent five years of side impact
evaluations, more than 80 percent of more than 200 vehicle makes and
models received the top ratings for injury mitigation for the rear seat
occupant, and that the proportion jumps to 95 percent for the most
recent two years of evaluations. IIHS explained that in these tests,
injury risk to rear-seat occupants is reduced by a combination of
vehicle countermeasures such as curtain air bags, door structural
improvements, and voluntary padding of the beltline. IIHS stated it
expects ``vehicle countermeasures that have improved outcomes for the
5th percentile female dummy in our testing

would also reduce the likelihood of injury to a 6-year-old seated in a
booster seat.''
---------------------------------------------------------------------------

    \93\ NHTSA proposed a 500 mm (19.6 in) beltline height for the
SISA. See, 79 FR at 4587-4588.
---------------------------------------------------------------------------

Agency Response
    After considering the comments and other available information,
NHTSA has adopted the proposed application of FMVSS No. 213a for the
reasons explained in the NPRM and further discussed below. Standard No.
213a will apply to add-on child restraint systems that are recommended
for use by children in a weight range that includes weights up to 18.1
kg (40 lb).\94\
---------------------------------------------------------------------------

    \94\ Harnesses and car beds are excepted from the standard.
---------------------------------------------------------------------------

    Several commenters suggested NHTSA adopt other test dummies to
expand the applicability of FMVSS No. 213a to CRSs for children
weighing more than 18.1 kg (40 lb). Safe Kids, Consumers Union (CU) and
Advocates urged NHTSA to develop a 6-year-old and/or 10-year-old child
side impact dummy. Safe Ride News (SRN) encouraged the agency to work
swiftly to adopt the Q6 dummy for use specifically in side impact
tests. Transport Research Laboratory (TRL) supported using the
omnidirectional Q-Series dummies used for side impact testing in United
Nations Economic Commission for Europe Regulation 129 (ECE R.129).\95\
TRL stated that the dummies were capable of distinguishing differences
in the design of child restraints, and that a Q6s (6-year-old child
dummy) has been developed, along with a side impact kit for the Q10
(10-year-old child dummy). ARCCA suggested NHTSA use the Hybrid III
(HIII) frontal impact 6-year-old dummy, and measure only head
containment and structural integrity. In contrast, Graco cautioned that
the use of larger test ATDs should be considered when they have been
confirmed to withstand side impact crash forces and have proven
biofidelity in the direction of a side collision.
---------------------------------------------------------------------------

    \95\ ECE R.129, ``Uniform provisions concerning the approval of
enhanced child restraint systems used on board vehicles (ECRS),''
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2013/R129e.pdf.
---------------------------------------------------------------------------

    NHTSA has decided against expanding the applicability of FMVSS No.
213a to child restraints recommended for children weighing more than
18.1 kg (40 lb). TRL suggested NHTSA consider the Q-series dummies
because they are currently used to test CRSs in United Nations Economic
Commission for Europe Regulation 129 (ECE R.129).\96\ NHTSA disagrees
with TRL. In 1999, First Technology Safety Systems (FTSS) \97\ deemed
the Q3 dummy's performance suboptimal in frontal testing, and even more
so in lateral. FTSS developed the Q3s dummy in response to the Q3's
suboptimal lateral performance. NHTSA has not evaluated the lateral
performance of the Q series 1-, 6- and 10-year-old dummies or Q series
side impact kits, but understands them to have the same shortcomings as
the original Q3. Given the unsatisfactory fundamental design of the Q
dummies, NHTSA decided not to use limited agency resources furthering
development of the Q-series 6- and 10-year-old dummies.\98\
---------------------------------------------------------------------------

    \96\ ECE R.129, ``Uniform provisions concerning the approval of
enhanced child restraint systems used on board vehicles (ECRS),''
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2013/R129e.pdf.
    \97\ In 2010, FTSS merged to become Humanetics Innovative
Solutions.
    \98\ NHTSA is developing the ``Large Omnidirectional Child
(LODC)'' 10-year-old child dummy, which is designed to have
biofidelic performance in lateral and frontal impact. Most of the
development work has been focused on frontal and oblique impacts.
NHTSA plans to evaluate and enhance the dummy for side impact
testing as well.
---------------------------------------------------------------------------

    ARCCA suggested that NHTSA use the HIII frontal 6-year-old dummy to
evaluate CRS structural integrity and head containment. The commenter
argued that NHTSA could use the HIII 6-year-old dummy since it will use
the 12-month-old frontal CRABI dummy in FMVSS No. 213a's side impact
test.
    NHTSA disagrees. As the agency explained in the NPRM, NHTSA decided
to use the frontal CRABI dummy because it would be fully restrained by
the child restraint on the SISA and no injury assessment reference
values would be taken. That is, the test with the fully restrained
frontal 12-month-old CRABI represents a best-case scenario for passing.
If a child restraint allowed the CRABI's head to contact the door under
these best-case circumstances, that would be a clear demonstration,
simply through observation of crash dynamics, that a child's head would
contact the door when involved in a real-world crash. Thus, while the
12-month-old CRABI dummy is not a side impact dummy, it could be
applied in a useful manner to evaluate aspects of CRS performance in
side impact. A failure to contain the 12-month-old CRABI's head would
lead to improved side impact designs (e.g., deeper side structure/wings
or shape changes in CRS adjustable head restraints).
    The same cannot be said about the frontal 6-year-old test dummy.
Children younger than 1-year of age have the highest use of CRSs with
internal harnesses (nearly 100 percent per National Child Restraint Use
Special Study (NCRUSS) \99\), so fully restraining the 1-year-old CRABI
in the test replicates how children will be restrained in the real
world. In contrast, only 8 percent of children 6 years of age are
restrained in CRSs with internal harnesses. If the HIII 6-year-old
child dummy were restrained as 6-year-old children are usually
restrained in the real world, it would be restrained in a booster with
only a lap and shoulder belt. Many current booster seats could fail a
head containment criterion when tested with a frontal 6-year-old dummy,
even if the head of the 6-year-old dummy were above the beltline and
therefore likely to interact with a side curtain air bag in an actual
vehicle. To accurately simulate the side impact crash environment in
such testing, a representation of the side air bag appears appropriate.
This rulemaking has not considered the implications of including a side
curtain air bag on the SISA and doing so is beyond the scope of this
final rule.
---------------------------------------------------------------------------

    \99\ NCRUSS https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812142.
---------------------------------------------------------------------------

    ARCCA believed that applying FMVSS No. 213a to child restraints for
children weighing up to 29.5 kg (65 lb) would better protect children
seated in far-side and center seating positions by preventing impact
with other occupants and CRSs adjacent to the child, and helping assure
they remain properly positioned in their restraint system. SRN believed
it is likely that shorter children do not gain the full protection of
side curtain air bags in the 18.1 to 29.5 kg (40 to 65 lb) weight
range. Neither commenter provided data to support their views.
    Advocates and others argued that MAP-21 does not limit improvements
only to the use of CRS by children who weigh less than 18.1 kg (40 lb).
NHTSA has determined that, while the language of section 31501(a) of
MAP-21 is broad enough to encompass a large universe of child restraint
systems, there are practical and technical reasons for applying the
dynamic side impact test only to CRSs designed to seat children in a
weight range that includes weights up to 18 kg (40 lb). First, the
seated height of children weighing more than 18 kg (40 lb) who are
restrained in child restraints is typically sufficient to take
advantage of the vehicle's side impact protection systems, such as side
curtain air bags. Thus, the safety need for Standard No. 213's dynamic
side impact requirements is attenuated for these CRSs. NHTSA has also
determined that the test procedure of FMVSS No. 213a may not be
appropriate for testing child restraints recommended for children

weighing more than 18.1 kg (40 lb). A 6-year-old in a child restraint
will interact with vehicle side structures differently than a 3-year-
old, particularly around the vehicle beltline and with respect to a
side curtain air bag. The side impact seating assembly used in FMVSS
No. 213a does not include a side curtain air bag. The agency is unable
to conclude the side impact test reasonably replicates a near-side
crash as would be experienced by a child weighing over 18.1 kg (40 lb)
in the real world, since the side curtain air bag, a key vehicle
countermeasure affecting injury outcome to occupants whose heads are
above the beltline, is not represented in the test.
    Second, there is no side impact dummy representative of children
larger than those represented by the Q3s that can reasonably be used to
test CRSs for children above 18 kg (40 lb) to the dynamic side impact
requirements in this final rule. As explained throughout this
rulemaking,\100\ without an appropriate test dummy, the data from a
dynamic test would not provide a meaningful assessment of the
performance of the CRS in protecting children of weights above 18.1 kg
(40 lb). For FMVSS No. 213's front-impact tests, NHTSA increased the
applicability of the standard to increasingly higher weight limits
gradually, and only when appropriate test dummies became available for
use in compliance testing, to ensure test data were meaningful and to
avoid giving a false sense of security about CRS performance. NHTSA is
developing the Large Omni-Directional Child ATD representative of a
seated 9- to 11-year-old child.\101\ When the development and
standardization process of this child dummy is complete, NHTSA will
consider a side impact test environment appropriate for evaluating CRSs
intended for use by older and larger sized children than those subject
to this final rule.
---------------------------------------------------------------------------

    \100\ See NPRM. 79 FR at 4572-4573.
    \101\ Suntay, B., Carlson, M., Stammen, J., ``Evaluation of the
Large Omni-Directional Child Anthropomorphic Test Device,'' DOT HS
812 755, July 2019. Evaluation of the Large Omni-Directional Child
Anthropomorphic Test Device (bts.gov).
---------------------------------------------------------------------------

    MAP-21 requires a final rule amending FMVSS No. 213, which means
that the rulemaking must be conducted in accordance with the Safety
Act. Under the Safety Act, NHTSA is authorized to prescribe Federal
motor vehicle safety standards that are practicable, meet the need for
motor vehicle safety, and are stated in objective terms.\102\ ``Motor
vehicle safety'' is defined in the Safety Act as ``the performance of a
motor vehicle or motor vehicle equipment in a way that protects the
public against unreasonable risk of accidents occurring because of the
design, construction, or performance of a motor vehicle, and against
unreasonable risk of death or injury in an accident, and includes
nonoperational safety of a motor vehicle.'' \103\ When prescribing such
standards, NHTSA must consider all relevant, available motor vehicle
safety information, and consider whether a standard is reasonable,
practicable, and appropriate for the particular type of motor vehicle
or motor vehicle equipment for which it is prescribed.\104\ NHTSA must
also consider the extent to which the standard will further the
statutory purpose of reducing traffic accidents and associated
deaths.\105\
---------------------------------------------------------------------------

    \102\ 49 U.S.C. 30111(a).
    \103\ 49 U.S.C. 30102(a)(8).
    \104\ 49 U.S.C. 30111(b).
    \105\ Id.
---------------------------------------------------------------------------

    NHTSA has developed a standard that will improve the protection of
children seated in child restraint systems during side impacts, in
accordance with MAP-21, while meeting the criteria of Section 30111 of
the Safety Act. For the reasons explained above, the agency believes
that FMVSS No. 213a meets the need for safety, is stated in objective
terms, and is reasonable, practicable, and appropriate.

e. Improving Side Impact Protection for Children Older Than 3-Years-Old

    To be clear, this final rule applying to child restraints for
children weighing up to 18.1 kg (40 lb) will significantly improve side
impact protection of most children up to age 6. According to the CDC
growth charts, about 100 percent of 3-year-old children, 75 percent of
4-year-old children, 50 percent of 5-year-old children, and 25 percent
of 6-year-old children weigh 18.1 kg (40 lb) or less.\106\ Child
restraints subject to this final rule can be used by all children 0- to
3-years of age, most 4-year-olds, half of 5-year-olds, and 25 percent
of 6-year-old children. This final rule improves the side impact
protection of all these children.
---------------------------------------------------------------------------

    \106\ Center for Disease Control (CDC) 2000 Growth Charts.
https://www.cdc.gov/growthcharts/cdc_charts.htm. Last Accessed
August 8, 2018.
---------------------------------------------------------------------------

    This final rule not only improves the side impact protection
offered by the safety seats but also increases the likelihood
caregivers will keep the children in the safety seats longer before
prematurely transitioning to a booster seat, which is an outcome that
improves child safety.\107\ Booster seats typically do not have
substantial side structure ``wings'' or an internal belt system to
restrain the child occupant, so it would be a technical challenge for
booster seats to meet the side impact requirements of this final rule.
However, because FMVSS No. 213a is written to apply specifically to
child restraints for children weighing less than 18.1 kg (40 lb),
manufacturers of booster seats will likely respond to this final rule
by marketing the seats as only suitable for children weighing more than
18.1 kg (40 lb) (so as to exclude the seats from meeting FMVSS No.
213a). NHTSA believes such a change that limits use of booster seats by
small children would benefit safety, as field data show that children
weighing less than 18.1 kg (40 lb) are safer in child safety seats than
in boosters.\108\ Thus, the 18.1 kg (40 lb) threshold will benefit
child passenger safety, as it will help keep children too small for
booster seats in child safety seats until they are ready for a booster
seat.
---------------------------------------------------------------------------

    \107\ NHTSA recommends that children riding forward-facing
should be restrained in CRSs with internal harnesses (child safety
seats) as long as possible before transitioning to a booster seat.
https://www.nhtsa.gov/equipment/car-seats-and-booster-seats#age-size-rec.
    \108\ NHTSA's November 2, 2020, NPRM, supra, also proposed that
booster seats must not be labeled for children weighing less than
18.1 kg (40 lb). 85 FR at 69427, col. 3. FMVSS No. 213 currently
permits booster seats only to be recommended for children weighing
at least 13.6 kg (30 lb) (S5.5.2(f)). Based on an analysis of field
data and other considerations, NHTSA proposed raising the 13.6 kg
(30 lb) value. We are concerned that 30 pounds corresponds to the
weight of a 50th percentile 3-year-old, and to the weight of a 95th
percentile 18-month-old; i.e., children too small to be safely
protected in a booster seat. In the November 2, 2020 NPRM, we
proposed to amend S5.5.2(f) to raise the 13.6 kg (30 lb) limit to
18.2 kg (40 lb), which is greater than the weight of a 97th
percentile 3-year-old (17.7 kg (39.3 lb)) and approximately the
weight of an 85th percentile 4-year-old.
---------------------------------------------------------------------------

    Further, this final rule will also benefit the side protection of
children weighing more than 18.1 kg (40 lb) in several ways. A review
of CRS models in the market suggests that most child restraints sold
for children weighing less than 18.1 kg (40 lb) are designed to also be
used by children weighing more than 18.1 kg (40 lb) as forward-facing
CRSs with harnesses and as booster seats.\109\ As the seated height
difference between a 3-year-old and a 6-year-old is only 3.5 inches,
the countermeasures used by the combination seat to protect children
weighing less than 18.1 kg (40 lb) could also benefit the older child
in the booster seat mode.\110\ The restraints

will have the same frame and can use the adjustable head protection and
side padding countermeasures provided to meet this final rule to
protect children weighing more than 18.1 kg (40 lb).
---------------------------------------------------------------------------

    \109\ These child restraints are commonly called ``combination
seats.'' They are sold for use with younger children (with a
harness) and older children (as a booster seat)
    \110\ This observation accords with NTSB's comment that ``the
proposed tests encompass the majority of CRSs because the upper use
limit for most small restraint systems extends to at least 40 pounds
and the lower use limit is at or below 40 pounds . . .'' ``We
recognize that children at weights less than or greater than 40
pounds benefit from the increased protection provided by a harnessed
CRS.''
---------------------------------------------------------------------------

    This final rule will also improve the side impact protection of
booster seats by better assuring that only children large enough (over
18.1 kg (40 lb)) to be protected by the side curtain air bag will use
the seats. NHTSA stated in the preamble to the NPRM that the height of
children weighing more than 18.1 kg (40 lb) seated in a CRS would be
sufficient to take advantage of the vehicle's side impact protection
systems, such as side curtain air bags.\111\ IIHS provided data
confirming that side curtain air bags can protect children weighing
over 18.1 kg (40 lb) seated in booster seats. The data show that the CG
of the head of a 6-year-old child seated in a booster seat is above the
beltline at 600-650 mm above the vehicle seat, and is within a few
centimeters of the position of the head of the 5th percentile adult
female test dummy. In IIHS's tests, the vehicles received the top
ratings for injury mitigation for the rear seat occupant represented by
the 5th percentile adult female test dummy, demonstrating the side
curtain air bags, door structural improvements, and padding of the
beltline were effective in protecting the 5th percentile adult female
in side impacts. IIHS's data indicate a 6-year-old in a booster is
situated in the rear seat similarly to a 5th percentile female, and
that both occupants will be positioned relative to the beltline and the
side curtain air bags in a manner that would enable them to benefit
from the vehicle countermeasures.
---------------------------------------------------------------------------

    \111\ 79 FR at 4573, col. 2.
---------------------------------------------------------------------------

    NHTSA has also reviewed more recent data IIHS presented at the 2018
Society of Automotive Engineers (SAE) Government Industry Meeting.\112\
The study showed that the HIII-6-year-old head CG in a high back
booster and a backless booster are above the beltline and are 33 and 64
mm lower, respectively, than that of the SID-IIs 5th percentile female
side impact dummy. These data again verify that a 6-year-old child in a
booster will be in-position to be protected by the vehicle's side
impact protection countermeasures, which include the side curtain air
bag and door structural improvements.
---------------------------------------------------------------------------

    \112\ The IIHS SAE Government Industry meeting presentation
titled ``Booster seat characteristics in the US market'' can be
found in the docket.
---------------------------------------------------------------------------

    Following on these findings, NHTSA measured the HIII 6-year-old
dummy in four booster seat models installed on the SISA and compared
its positioning with the SID-IIs dummy seated directly on the SISA. The
booster seats were the Evenflo Chase and the Graco Nautilus (high back
boosters), and the Harmony Youth and the Graco Affix (backless
boosters). The measurements show that the HIII 6-year-old dummy's head
CG, when seated in the highest booster seat (Graco Nautilus 65) is 1 mm
higher than that of the SID-IIs dummy seated on the SISA, and less than
5 cm (47.5 mm) lower than the SID-IIs dummy's head when seated in the
shortest booster seat (Graco Affix). All head CGs were above the
beltline (see Figure 2).
[GRAPHIC] [TIFF OMITTED] TR30JN22.005

    These data confirm the similarity between the head position of the
6-year-old dummy seated in a booster seat and that of the 5th
percentile female dummy. FMVSS No. 226 ejection mitigation phase-in
requirements were completed in September 2017. Thus, not only will all
new vehicles have side curtain air bag technologies that will protect
these older children in booster seats, but most of the fleet will
incorporate these technologies by the

compliance date of this final rule. The technologies can benefit older
and larger children weighing more than 18.1 kg (40 lb) or with a
stature of more than 1100 mm (43.3 inches) when the children are
properly positioned by a typical booster seat.
    The safety of booster seats will be directly improved by assuring
that only children large enough to be protected by the side curtain air
bag will use the seats. Until this final rule, booster seats could be
labeled for children with weights as low as 13.6 kg (30 lb).
Restricting booster seat use instructions to children weighing more
than 18.1 kg (40 lb) will help ensure they will be used only by
children large enough to take advantage of a vehicle's side protection
countermeasures. Booster seats have been shown to be highly beneficial
in frontal crashes, and are needed to transition children from safety
seats to a vehicle belt system. This final rule increases the safety of
booster seats by enhancing their utility in side impacts, in
furtherance of MAP-21's mandate to improve the protection of children
seated in child restraint systems during side impacts.
    Since the NPRM's publication in 2014, NHTSA has seen a few booster-
seat models that provide a lower than typical boosting height (the
height that a booster seat raises a seated child), which may not raise
the height of children weighing more than 18.1 kg (40 lb) sufficiently
to take advantage of the vehicle countermeasures. Subsequently, NHTSA
sponsored a research program \113\ as a first step toward determining a
minimum boosting height for CRSs recommended for children weighing more
than 18.1 kg (40 lb) to ensure that these children can benefit from the
vehicle countermeasures and that the CRSs provide enough lift to
position the child properly relative to the vehicle's lap and shoulder
belts. More on this research is discussed at a later section of this
final rule.
---------------------------------------------------------------------------

    \113\ Klinich, Kathleen D., Jones, Monica H., Manary, Miriam A.,
Ebert, Sheila H., Boyle, Kyle J., Malik, Laura, Orton, Nichole R.,
Reed, Matthew P., (2020, April). Investigation of potential design
and performance criteria for booster seats through volunteer and
dynamic testing (Report No. DOT HS 812 919). Washington, DC:
National Highway Traffic Safety Administration. Link: https://rosap.ntl.bts.gov/view/dot/49119.
---------------------------------------------------------------------------

f. Weight as a Limiting Factor

    Advocates stated ``a discussion of why weight alone is being
proposed as a limitation should be provided, considering the repeated
discussion of the obesity problem facing the nation's youth and the
agency's acknowledgement that seated height, rather than weight alone,
is the determining factor.''
Agency Response
    The applicability of the standard is not only based on the child
weight recommendation for use of the CRS but also on the child height
recommendation. The NPRM proposed in S3 to apply the standard to ``add-
on child restraint systems, except for harnesses and car beds, that are
recommended for use by children in a weight range that includes weights
up to 18.1 kg (40 lb), or by children in a height range that includes
children whose height is not greater than 1100 mm.'' \114\ This final
rule adopts the proposed S3. Additionally, the dummy selection for side
impact dynamic testing is made taking into consideration weight and
height. Any CRS that is recommended for children weighing between 13.6
kg (30 lb) (corresponding to a 95th percentile 18-month-old) and 18.1
kg (40 lb) (corresponding to a 85th percentile 4-year-old) or a height
between 870 mm (34.3 inches) (corresponding to a 95th percentile 18-
month-old) and 1100 mm (43.3 inches) (corresponding to a 97th
percentile 4-year-old) will be tested with the Q3s dummy (see Table
15).
---------------------------------------------------------------------------

    \114\ 79 FR at 4601.

                                                 Table 15--Comparison of Weight and Height by Percentiles for Young Children and Child ATDs 115
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Weight kg (lb)                                                   Height mm (in)
                          Percentiles                          ---------------------------------------------------------------------------------------------------------------------------------
                                                                    3rd         5th        50th         95th         97th         3rd          5th          50th          95th          97th
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
12 MO Child...................................................  8.1 (18.1)  8.3 (18.5)    9.9 (22)  11.9 (26.4)  12.2 (27.2)        697.1        703.2  750.6 (29.6)  800.2 (31.5)  807.5 (31.8)
                                                                                (27.4)       (27.7)
12 MO CRABI...................................................  ..........  ..........         9.9  ...........  ...........  ...........  ...........         740.4  ............  ............
                                                                                (22.05)                                                           (29.15)
18 MO Child...................................................  9.3 (20.7)  9.5 (21.2)        11.3  13.5 (30.1)      14 (31)        753.6   761.1 (30)  814.4 (32.1)  868.2 (34.2)  875.9 (34.5)
                                                                                (25.2)                                 (29.7)
18 MO CRABI...................................................  ..........  ..........        11.1  ...........  ...........  ...........  ...........  817.9 (32.2)  ............  ............
                                                                                (24.7)
24 MO Child...................................................        10.1   10.4 (23)        12.3  14.8 (32.9)  15.3 (33.9)        800.5   809 (31.9)  866.9 (34.1)  924.8 (36.4)  933.8 (36.8)
                                                                    (22.5)                  (27.4)                                 (31.5)
36 MO Child...................................................        11.4        11.9   13.9 (31)  17.2 (38.1)  17.7 (39.3)        875.9        884.9  947.4 (37.3)        1013.8        1023.7
                                                                    (25.4)      (26.4)                                             (34.5)       (34.8)                      (39.9)        (40.3)
Q3s...........................................................  ..........  ..........   14.5 (32)  ...........  ...........  ...........  ...........    978 (38.5)  ............  ............
48 MO Child...................................................        12.9        13.2   16 (35.5)  20.2 (44.8)  46.6 (46.6)        936.5        946.4   1015.8 (40)        1087.7        1098.2
                                                                    (28.7)      (29.4)                                             (36.9)       (37.3)                      (42.8)        (43.2)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    The commenter's reference to ``the obesity problem facing the
nation's youth'' was not clear, but it could be that Advocates was
arguing that the standard should apply to child restraints for children
weighing more than 18.1 kg (40 lb). NHTSA disagrees with increasing the
40-lb threshold because the absence of a test dummy to test the side
impact protection provided to heavier children makes raising the
threshold non-evidence based and could provide a false sense of
security about the protection afforded to the larger children. This
issue is discussed at length in the section discussing the scope of the
new standard.
---------------------------------------------------------------------------

    \115\ Center for Disease Control (CDC) 2000 Growth Charts.
https://www.cdc.gov/growthcharts/cdc_charts.htm... Last Accessed
August 8, 2018.
---------------------------------------------------------------------------

g. Labeling CRSs for Children Weighing Over 18.1 kg (40 lb)

1. Label as ``Not Tested in Side Impacts''
Comments Received
    Advocates commented that booster seats designed for children
weighing more than 18.1 kg (40 lb) should be labeled to provide parents
with a warning that their child may not be protected in a side crash.
Advocates stated that the warning should indicate ``this CRS has not
been tested in side impacts for the protection of children weighing
more than 18.1 kg (40 lb).'' Similarly, a law student group suggested
there should be labeling or consumer information on the packaging of
CRSs informing consumers that the CRS has not been tested for side
impact crashes for children weighing more than 18.1 kg (40 lb).
Agency Response
    NHTSA has carefully considered the request but declines to adopt
such a requirement in this final rule. The issue was not discussed in
the NPRM, and NHTSA would like the benefit of more public discourse on
the ramifications of such a requirement. NHTSA highly values consumers'
knowing how child restraints can protect their children's safety.
However, information provided

on or with child restraints must be carefully worded so as not to
confuse caregivers or cause unintended responses to it. For example,
the agency is concerned that a statement such as, ``This CRS has not
been tested in side impacts for the protection of children weighing
more than 18.1 kg (40 lb)'' may be interpreted by some as saying the
CRS is not regulated in any way under any Federal standard, since an
average consumer is unlikely to know the applicability or extent of
FMVSS No. 213 versus FMVSS No. 213a. Before adopting such a labeling
requirement, NHTSA should evaluate the risk that a caregiver might
respond to the label by deciding to forgo use of a booster seat or
other CRS entirely when the child reaches 18.1 kg (40 lb). Such an
outcome would lead to a degradation of child passenger safety. NHTSA is
also concerned that the statement might dampen efforts on the part of
researchers and engineers to develop potential improvements to side
impact protection for older children, such as by developing data-driven
countermeasures using methods (e.g., mathematical models along with
human body models) that simulate the side impact test of this final
rule.
2. Head Under Window Sill
    Advocates suggested that instructions to parents (either in vehicle
manuals or other sources) should indicate that children below a certain
height, or whose head does not reach entirely above the sill of the
vehicle window, should be restrained properly in a safety seat since
they may not be afforded protection by side impact safety requirements
designed to protect adults. The commenter suggested that a similar form
of diagram and wording on booster seats for taller and/or heavier
children would also assist parents in selecting the proper seating
method to ensure protection. The law students suggested that the
packaging should indicate that children whose heads do not reach above
the windowsill should be restrained in a CRS.
Agency Response
    NHTSA is declining these suggestions to adopt the measures in this
final rule. The agency would like to know more about the need for such
instructions and their effectiveness. NHTSA is conducting a research
program to determine a minimum boosting height for CRSs recommended for
children weighing more than 18.1 kg (40 lb). As a first step, NHTSA
evaluated the boosting height of current booster seat designs
recommended for children weighing more than 18.1 kg (40 lb). The
evaluation included posture and belt fit measures for 24 child
volunteers aged 4 to 12 seated in six different booster seat models
that were installed in 3 different vehicle models and in laboratory
seating conditions representing the range of cushion lengths and belt
geometries in later model vehicle rear seats.\116\ Among the program's
next steps, the research will seek to determine whether CRS seating
platforms should be at least a minimum height to position the head of
the child high enough to benefit from vehicle side impact protection
countermeasures. If a minimum boosting height can be determined, NHTSA
may consider rulemaking to specify a minimum boosting height. Results
from NHTSA's research will help inform the agency as to whether the
suggested warning label is merited for some CRSs.
---------------------------------------------------------------------------

    \116\ Klinich, Kathleen D., Jones, Monica H., Manary, Miriam A.,
Ebert, Sheila H., Boyle, Kyle J., Malik, Laura, Orton, Nichole R.,
Reed, Matthew P., (2020, April). Investigation of potential design
and performance criteria for booster seats through volunteer and
dynamic testing (Report No. DOT HS 812 919). Washington, DC:
National Highway Traffic Safety Administration. Link: https://rosap.ntl.bts.gov/view/dot/49119.
---------------------------------------------------------------------------

VII. Aspects of the FMVSS 213a Test Procedure

    NHTSA developed this final rule to replicate a vehicle-to-vehicle
intersection crash. NHTSA explained in the NPRM that this side impact
is best replicated in a test procedure that reflects the dynamic
elements of both the striking and struck vehicle in the crash. NHTSA
stated that a side impact test procedure should account for: (1) the
struck vehicle door velocity prior to the interaction of the striking
vehicle with the door sill of the struck vehicle, (2) the acceleration
profile of the struck vehicle, and (3) the impact angle to replicate
the longitudinal component of the direction of force. NHTSA concluded
that basing the specification of these parameters on actual vehicle
crash characteristics would enable the realistic simulation of the
relative velocity between the intruding door and the CRS. Accordingly,
the agency developed FMVSS No. 213a to simulate a full-scale vehicle-
to-vehicle side impact based on the MDB requirements of FMVSS No. 214,
``Side impact protection.'' \117\
---------------------------------------------------------------------------

    \117\ As explained above in this document, FMVSS No. 214
specifies performance requirements for the protection of occupants
in side impact crashes. In a full-scale crash test representing a
severe intersection collision between two passenger vehicles, FMVSS
No. 214 requires passenger vehicles to protect occupants when the
vehicle is struck on either side by an MDB simulating an impacting
vehicle. The FMVSS No. 214 MDB crash test involves an MDB weighing
1,360 kg (3,000 lb), to represent a vehicle which is traveling at
48.3 kilometers per hour (km/h) (30 miles per hour (mph)) striking
the side of another vehicle which is traveling at 24 km/h (15 mph).
In the FMVSS No. 214 test, only the striking ``vehicle,''
represented by the MDB, is moving. Using vector analysis, the agency
combined the impact speed and impact angle data in crash files to
determine that the dynamics and forces of a crash in which a vehicle
traveling at 48.3 km/h (30 mph) perpendicularly strikes the side of
a vehicle traveling at 24.1 km/h (15 mph) could be represented by a
test configuration in which: the test vehicle is stationary; the
longitudinal centerline of the MDB is perpendicular to the
longitudinal centerline of the test vehicle; the front and rear
wheels of the MDB are crabbed at an angle of 27 degrees to the right
of its longitudinal centerline in a left side impact and to the left
of that centerline in a right side impact; and the MDB moves at that
angle and at a speed of 54 km/h (33.5 mph) into the side of the
struck vehicle.
---------------------------------------------------------------------------

Introduction

    To simulate the side impact crash for purposes of testing CRS
performance, NHTSA proposed using a dynamic sled test based on an
acceleration sled system \118\ that was developed by Takata.\119\ The
Takata procedure is based on an acceleration sled with a test buck
consisting of a sliding ``vehicle'' seat (representative of a rear seat
designated seating position) mounted to a rail system, along with a
``side door'' structure rigidly mounted to the sled buck structure.
Aluminum honeycomb is mounted below the side door structure. The side
door is made to reach a desired velocity prior to the aluminum
honeycomb contacting the sliding ``vehicle'' seat structure. Together,
the sliding seat and door structure are referred to as the side impact
seat assembly (SISA). Figure 3 shows the Takata sled system test
procedure.
---------------------------------------------------------------------------

    \118\ An acceleration sled is accelerated from rest to a
prescribed acceleration profile to simulate the occupant compartment
deceleration in a crash event. In comparison, a ``deceleration
sled'' is first accelerated to a target velocity and then is
decelerated to a prescribed deceleration profile to simulate the
same event.
    \119\ See Docket No. NHTSA-2007-26833-0023 for a transcript of
the February 8, 2007 meeting where Takata gave a presentation on its
side impact test procedure. NHTSA also published two papers on the
agency's research and testing on the Takata test procedure (Sullivan
(2009) and Sullivan (2011), discussed infra).
---------------------------------------------------------------------------

BILLING CODE 4910-59-P

[GRAPHIC] [TIFF OMITTED] TR30JN22.006

BILLING CODE 4910-59-C
    NHTSA conducted three studies in advance of the NPRM to identify
test parameters that would adapt the Takata sled system for use in
FMVSS No. 213a. NHTSA's 2009 Initial Evaluation of Child Side Impact
Test Procedures \120\ used a modified Takata test buck to

develop test parameters that would simulate the FMVSS No. 214 test
procedure. The selected parameters were based on ten vehicles that had
previously been tested in accordance with FMVSS No. 214 and a series of
four full-scale crash tests. NHTSA concluded that the sled test
procedure appeared to be repeatable and could distinguish between child
restraint models using some of the injury measures. Comparison of
results from side impact sled tests using the Q3s dummy with comparable
full-scale vehicle side impact crash tests indicated that the dummy
responses exhibited similar trends in the sled and full vehicle crash
tests. NHTSA also announced its intention to perform further sled
testing to refine test parameters such as door stiffness and geometry,
and to further assess issues such as the effect of an armrest on CRS
kinematics and dummy responses.
---------------------------------------------------------------------------

    \120\ Sullivan, L.K., Louden, A.E., ``NHTSA's Initial Evaluation
of Child Side Impact Test Procedures,'' 21st International
Conference on the Enhanced Safety of Vehicles, Paper No. 09-0539,
2009 [hereinafter Sullivan et al. (2009)].
---------------------------------------------------------------------------

    The follow up to NHTSA's initial evaluation, NHTSA's 2011
Evaluation of a Potential Side Impact Test Procedure,\121\ presented
subsequent tests and vehicle surveys conducted to determine
characteristics of various components of side impact test bucks such as
the seat cushion, door panel, and an armrest that would result in
improved real world representation of the side impact sled test
procedure.
---------------------------------------------------------------------------

    \121\ Sullivan, L.K., Louden, A.E., Echemendia, C.G. ``NHTSA's
Evaluation of a Potential Child Side Impact Test Procedure'' 22nd
International Conference on the Enhanced Safety of Vehicles, ESV
Paper No. 2011-0227, 2011 [hereinafter Sullivan et al. (2011)].
---------------------------------------------------------------------------

    NHTSA also conducted a vehicle survey \122\ to examine the geometry
and contact characteristics of vehicle rear seats in order to select
the geometry and material characteristics necessary to replicate the
physical environment of a typical rear seat in a side impact test. The
2012 Vehicle Rear Seat Study recorded measurements of 43 individual
rear seating position in 24 model year 2010 vehicles to obtain
dimensional characteristics of rear seat attributes that could affect
the performance of CRS in the rear seat compartment. In addition, NHTSA
surveyed the features of vehicle child restraint anchorage systems in
furtherance of the agency's data on the systems. As discussed further
below, NHTSA relied on these measurements to create a rear seat
environment for the SISA that represented vehicles in the modern fleet.
---------------------------------------------------------------------------

    \122\ Aram, M.L., Rockwell, T., ``Vehicle Rear Seat Study,''
Technical Report, July 2012. Docket No. NHTSA-2014-0012, Item No.
0005 (hereinafter 2012 Vehicle Rear Seat Study).
---------------------------------------------------------------------------

    NHTSA's studies showed that the Takata-based test procedure
demonstrated versatility for tuning parameters to obtain the desired
test environment. NHTSA could tune the parameters to simulate the two-
vehicle side crash replicated in the MDB test of FMVSS No. 214. NHTSA
also noted that the test could be easily modified to change the impact
angle to introduce the longitudinal crash component present in the
FMVSS No. 214 tests. In addition, in its preliminary evaluation of the
Takata test protocol, after making minor modification to the test
parameters \123\ NHTSA determined that the test procedure was
repeatable and could provide results that distinguished between the
performance of various CRS models based on the design of the side wings
and stiffness of the CRS padding.\124\
---------------------------------------------------------------------------

    \123\ Sullivan et al. (2009).
    \124\ Sullivan et al. (2011).
---------------------------------------------------------------------------

    Accordingly, based on the agency's research, NHTSA proposed a side
impact test for FMVSS No. 213a based on a refined and improved Takata
sled design. In addition, the NPRM proposed test specifications
developed by NHTSA ensuring the test procedure appropriately simulates
the FMVSS No. 214 MDB test, including the velocity of the striking
vehicle, the struck vehicle and the intruding door. Specifically, the
NPRM proposed the following specifications of the sled test to simulate
the FMVSS No. 214 MDB impact test of a small passenger car with the
child dummy restrained in a CRS positioned in the rear seat near-side
of the impact:
    1. The test buck consists of a sliding seat mounted to a rail
system along with a ``side door'' structure rigidly mounted to the sled
buck structure. The sliding seat and side door are representative of
today's passenger vehicles. The sliding seat of this ``side impact seat
assembly'' (SISA) is positioned sufficiently away from the side door to
allow the sled to reach a desired velocity (31.3 km/h) prior to the
time the sliding seat starts to accelerate to a specific acceleration
profile.
    2. The center of the CRS is positioned 300 mm from the edge of the
sliding seat next to the intruding door (simulating a near-side
position). At the time the sliding seat starts to accelerate, the
armrest on the door is located 32 mm (1.3 inches) from the edge of the
seat towards the CRS.
    3. CRSs would be installed on the sliding seat using CRAS. Belt-
positioning seats covered by the NPRM would be tested using a lap and
shoulder belt on the sliding seat of the SISA.
    4. NHTSA proposed injury criteria (expressed in terms of HIC15 and
chest deflection) for the Q3s. We proposed just to require head
containment of the 12-month-old CRABI (assess the ability of the CRS to
prevent the ATD's head from contacting the intruding door of the SISA).
In addition, the NPRM proposed to require CRSs to meet structural
integrity requirements when tested with the respective ATDs, and other
assorted performance criteria for belts and buckles.

a. Overview

    In this final rule, NHTSA finalizes a test procedure that builds on
the SISA and test specifications proposed in the NPRM. The agency has
adjusted the final test procedure from that proposed in the NPRM, after
considering the comments, results of additional testing of the SISA,
and the agency's work on the proposed FMVSS No. 213 frontal test
procedures.\125\ As discussed further below, we modified the SISA to
minimize variability in installation, make the SISA equipment more
durable, and better match the proposed frontal FMVSS No. 213 seat
assembly. In addition, we further specified some of the side test
parameters, including a relative door velocity profile and the distance
of the door armrest to the vehicle seat, to improve the repeatability
and reproducibility of the test procedure. The final SISA and test
specifications are discussed below in turn.
---------------------------------------------------------------------------

    \125\ See NPRM, 85 FR 69388, November 2, 2020, supra.
---------------------------------------------------------------------------

b. Side Impact Seat Assembly Characteristics

    The side impact seat assembly (SISA) consists of a sliding
``vehicle'' seat mounted to a rail system, along with a side door
structure rigidly mounted to the sled buck structure. In the NPRM,
NHTSA described the agency's efforts to ensure that the sliding
``vehicle'' seat and side door would be representative of today's
passenger vehicles. Both NHTSA's initial evaluation studies and the
2012 Vehicle Rear Seat Study, discussed above, examined the geometry
and contact characteristics of present-day vehicle rear seats. The
agency used this information to design a seat assembly with the
geometry and material characteristics that were necessary to replicate
the physical environment of a typical rear seat relevant to the side
impact test. NHTSA identified the following rear seat features to
replicate in the SISA: (1) rear seat geometry (seat back angle, seat
pan angle, beltline height from approximately the vehicle seat bight
(i.e., the intersection of the seat cushion

and the seat back), height of the top of the armrest (from the seat
bight)), (2) rear seat cushion stiffness, and (3) door shape (height of
window, armrest thickness (protrusion of the armrest from the door
\126\)) and padding.
---------------------------------------------------------------------------

    \126\ The original Takata sled buck did not include an armrest.
NHTSA modified the sled buck to include an armrest.
---------------------------------------------------------------------------

    In addition, NHTSA performed a series of sled tests as a
sensitivity analysis to better understand the effect of the sled system
configuration on dummy responses.\127\ The parameters evaluated were
the seat cushion stiffness, door padding stiffness, presence of
armrest, and windowsill height.
---------------------------------------------------------------------------

    \127\ Sullivan et al. (2011).
---------------------------------------------------------------------------

    Based on the agency's research, NHTSA proposed using a SISA for the
FMVSS No. 213a test procedure that modified aspects of the original
Takata sled specifications to make the SISA better represent the rear
seat environment. Figure 4 shows the proposed SISA.
[GRAPHIC] [TIFF OMITTED] TR30JN22.007

    The proposed SISA had the following specifications:
     A single seating position representing a rear outboard
seating position.
     Seat back and seat pan angles of 20 and 15 degrees,
respectively, which is the same as the original Takata buck. Both
angles were well within the ranges found in NHTSA's vehicle survey, and
those angles were the same as the ECE R.44 bench seat.
     ECE R.44 rear seat cushion foam. NHTSA proposed using this
foam because it was more representative of the stiffness of current
rear seats in the vehicle fleet than other cushion foams surveyed
(FMVSS No. 213, NPACS). However, NHTSA also noted that sensitivity
studies showed seat foam cushion stiffness had little effect on dummy
responses in the side impact test procedure.
     A 64 mm (2.5 inches) thick armrest attached to a 51 mm (2
inches) thick door panel. The armrest was a ``stiff'' foam (United Foam
#4), attached to an ``average'' stiffness foam padding door (Ethafoam
220). NHTSA stated that this configuration appeared to be
representative of the rear seat environment, and the armrest stiffness
using the ``stiff'' United Foam #3 was within the range of armrest
thickness of surveyed vehicles. Importantly, dummy responses with this
armrest/door configuration were similar to those seen in vehicle crash
tests.\128\
---------------------------------------------------------------------------

    \128\ Sullivan et al. (2011).
---------------------------------------------------------------------------

     A beltline height of 500 mm (19.6 inches). Although this
value was slightly higher than the average beltline height of vehicles
surveyed (489 mm), NHTSA proposed the 500-mm value to ensure that the
proposed side impact test was sufficiently stringent to account for
vehicle beltlines that were higher than the average value.
     Lower anchorages of the CRAS symmetrically located on
either side of the centerline of the simulated outboard seating
position of the SISA bench seat. The location of the top tether
anchorage was on the lower rear frame of the seat, similar to the
typical location of a tether anchorage in captain's seats in minivans.
    In addition to these aspects of the SISA that the agency discussed
in the preamble, NHTSA included detailed drawings of the SISA in the
docket for the NPRM, which further specified materials and measurements
of every part of the SISA.
    While NHTSA welcomed comments on all aspects of the proposed rule,
the agency sought comment on specific aspects of the SISA, including
the proposed seat cushion foam and seat

cushion assembly. In addition, NHTSA had stated the agency had
initiated a research program to evaluate how the test parameters of the
FMVSS No. 213 frontal sled test should be updated to reflect any
significant real-world developments.\129\ The agency stated it planned
to develop a test bench seat with seat cushion stiffness that has
characteristics of seat cushions in recent vehicle models, pursuant to
MAP-21's mandate to amend the standard seat assembly specifications
under FMVSS No. 213's frontal test ``to better simulate a single
representative motor vehicle rear seat.'' \130\ NHTSA stated in the
NPRM for side impact \131\ that it would consider, to the extent
possible under the timeframes for the research and rulemaking programs,
the merits of using this updated frontal test seat cushion foam in the
side impact sled.
---------------------------------------------------------------------------

    \129\ NHTSA Vehicle Safety and Fuel Economy Rulemaking and
Research Priority Plan 2011-2013 (Docket No. NHTSA-2009-0108-0032).
    \130\ Quoting MAP-21, Sec.  31501(b), ``Frontal Impact Test
Parameters.''
    \131\ 79 FR at 4586, col. 2.
---------------------------------------------------------------------------

    Since publication of the 2014 NPRM, NHTSA continued to develop a
standard seat assembly for upgrading the FMVSS No. 213 frontal impact
sled test using the SISA sliding seat as a starting point. The November
2, 2020 NPRM proposing amendments to FMVSS No. 213 described the
agency's continued work updating aspects of the vehicle rear seat
environment, such as the seat back height, seat cushion stiffness, and
CRAS and seat belt anchorage locations, so that the frontal impact seat
assembly would be more representative of vehicle rear seats. The
proposed standard seat assembly for the frontal impact sled test is
similar to the proposed SISA sliding seat, although the proposed
frontal impact seat assembly has some more up-to-date specifications
for features such as the seat cushion thickness, seat back height and
anchorage locations. These differences were described in detail in the
November 2, 2020 NPRM.\132\
---------------------------------------------------------------------------

    \132\ 85 FR at 69393.
---------------------------------------------------------------------------

    In the November 2020 NPRM, NHTSA sought comment on whether the side
impact test seat assembly and the seat assembly proposed in the 2020
NPRM should be consistent.\133\ NHTSA stated in the November 2, 2020
NPRM that using the same specifications of the standard seat assembly
(including seat geometry, seat cushion, and anchorage locations) for
both the side impact test and a frontal impact test would make sense,
since the agency is seeking to test CRSs on a representative seat
assembly and the same passenger vehicles are involved in side and
frontal crashes.
---------------------------------------------------------------------------

    \133\ Id., col. 2-3.
---------------------------------------------------------------------------

    The agency also stated that the standard seat assembly proposed in
the January 2014 side impact NPRM is substantially like the seat
proposed in the November 2020 NPRM, but that NHTSA believes the seat
assembly proposed in the November 2020 NPRM is a better seat assembly
primarily regarding the cushion foam. NHTSA explained that the January
2014 NPRM specified use of the ECE R.44 seat cushion, while the
November 2020 proposed seat assembly incorporates seat cushion foam
that is more representative of the seat cushion stiffness of the
current vehicle fleet. NHTSA stated that the proposed seat cushion ``is
also easier to procure than the ECE R.44 foam. Commenters to the
January 2014 side impact NPRM expressed concerns about the difficulty
to source the ECE R44 seat foam, which is only available from one
overseas supplier. [Footnote omitted.] NHTSA tentatively believes that
using the foam specified in this NPRM for the frontal test seat
assembly would alleviate those concerns.''
    Four commenters (Evenflo, Cybex, Graco and Consumer Reports) to the
November 2, 2020 frontal upgrade NPRM expressed support for having
consistent side and frontal impact test seat assemblies in FMVSS No.
213 and FMVSS No. 213a, respectively. Evenflo noted that using the same
seat assembly in both test methods will reduce variables in assessing a
CRSs. Cybex commented that having a more representative seat assembly
as the one proposed for the frontal impact sled test would be
beneficial to real-world crashworthiness. No commenter opposed having
consistency between the seat assembly used in the frontal and side
impact sled tests.
    NHTSA is moving forward with a SISA that differs from the 2014
proposed SISA in some respects to make it more representative of rear
seats in the current vehicle fleet, to address comments, and to better
align the SISA with the proposed seat assembly for the FMVSS No. 213
frontal impact test. These structural changes and the agency's
responses to other comments on the SISA are discussed in detail, below.
Other minor modifications, like minor changes to accelerometer
placement and the addition of stiffening structures to reduce
vibrations, are discussed more at length in the ``FMVSS No. 213 Side
Impact Test Evaluation and Revision'' report included in the docket for
this final rule.\134\
---------------------------------------------------------------------------

    \134\ Louden & Wietholter (2022).
---------------------------------------------------------------------------

    NHTSA believes that the above modifications make the SISA better
representative of the rear seat environment and better able to
reproduce the characteristics of a side impact. In addition, these
modifications address comments on the availability and durability of
materials used in the SISA, and address comments on repeatability and
reproducibility of the final test procedure. Importantly, and as
discussed further below, NHTSA performed tests with the final SISA
configuration to compare the test results with those using the proposed
SISA, and concluded that test results with the updated SISA in this
final rule are not significantly different from those with the proposed
SISA. The following sections discuss comments on aspects of the sliding
seat, door, and maintenance of the SISA.
1. Seat Characteristics
i. Rear Seat Cushion Stiffness
    To determine the stiffness of the seat foam for the proposed SISA,
NHTSA considered several data points. We considered the vehicle survey
that measured the rear seat cushion stiffness of 13 vehicles, as well
as the seat cushion stiffness of the seat cushions used in FMVSS No.
213, the United Nations Economic Commission for Europe, ``Uniform
provisions concerning the approval of restraining devices for child
occupants of power-driven vehicles (child restraint systems)'' (ECE
R.44), and the New Programme for the Assessment of Child Restraint
Systems (NPACS) \135\ programs.\136\ The results of the survey showed
that the FMVSS No. 213 foam was softer than all the vehicle seat foams
surveyed. The ECE R.44 and NPACS foams were stiffer than the FMVSS No.
213 foam, and more representative of the vehicles surveyed. However,
NHTSA's sensitivity analysis to determine the effect of the seat
cushion stiffness on dummy readings and CRS performance showed that
seat cushion foam stiffness had little effect

on the dummy responses in these side impact tests.
---------------------------------------------------------------------------

    \135\ The NPACS consortium was funded in 2005 by governments of
the United Kingdom, the Netherlands, Germany, the Generalitat of
Catalonia, and five non-governmental organizations. The objective of
NPACS is to provide scientifically based EU wide harmonized test and
rating protocols to offer consumers clear and understandable
information about dynamic performance and usability of child
restraint systems. NPACS is similar to NHTSA's New Car Assessment
Program (NCAP), and to the NCAP program administered in Europe
(EuroNCAP), in that NPACS is a voluntary consumer information
program, rather than a binding regulation. (Note, however, that
NPACS is designed to test CRSs, while NCAP focuses on vehicle
performance.)
    \136\ Sullivan et al. (2011).
---------------------------------------------------------------------------

    Accordingly, NHTSA initially proposed that the seat cushion foam
for the SISA have the stiffness of the ECE R.44 seat foam, given that
the ECE R.44 foam was more representative of the current rear seats in
the vehicle fleet than the FMVSS No. 213 cushion foam. At that time,
NHTSA had not yet developed the NHTSA-Woodbridge seat cushion foam, so
NHTSA stated that the agency preferred the ECE R.44 foam over the NPACS
foam because although the two foams were similar in stiffness, the ECE
R.44 foam was more readily available than the NPACS foam. NHTSA invited
comment on this proposed seat cushion foam and seat cushion assembly.
    NHTSA also stated that the agency had initiated a research program
to evaluate how the test parameters of the FMVSS No. 213 frontal sled
test should be updated to reflect any significant real-world
developments. Within this program, NHTSA planned to develop a test
bench seat with seat cushion stiffness characteristic of seat cushions
in recent vehicle models. NHTSA stated that the agency would consider,
to the extent possible under the timeframes for the research and
rulemaking programs, the merits of using this updated seat cushion foam
in the side impact sled.
Comments Received
    CU, Dorel, Graco and UPPAbaby commented that the ECE R.44 foam was
appropriate for side impact testing. CU and UPPAbaby also suggested
including the same foam in the FMVSS No. 213 frontal impact test. CU
added that the ECE R.44 foam should be used in the frontal impact FMVSS
No. 213 test because a stiffer standard seat foam may result in larger
performance differences among CRSs than that with the current standard
seat assembly in the FMVSS No. 213 frontal impact test.
    Relatedly, while MGA did not provide specific comments on the
proposed seat foam, MGA did state that there are few areas where FMVSS
No. 213 and FMVSS No. 213a could be harmonized with regards to the seat
cushion. Specifically, MGA stated that the cover material, foam insert,
and overall assembly for the seat cushion could be harmonized,
referencing FMVSS No. 213's leather type zippered cover over two softer
pieces of foam, compared to the FMVSS No. 213a's cloth type cover
wrapped over a single piece of stiffer foam. Similarly, Graco requested
that NHTSA consider the use of the same foam for frontal crash testing
as used in side testing in any future improvements to FMVSS No. 213.
    An individual, Mr. Hauschild, commented that the seat foam needs to
be representative of the current vehicle fleet, and added that research
has shown that the foam of the FMVSS No. 213 standard seat assembly for
forward-facing seat testing reacts differently than vehicle
manufacturer seats and can influence the performance of the CRS (citing
Tylko et al., 2013 \137\). Graco agreed with the use of standard seat
foam that is more representative of current vehicles.
---------------------------------------------------------------------------

    \137\ Tylko, S., Locey, C.M., Garcia-Espana, J.F., Arbogast,
K.B., & Maltese, M.R. 2013. Comparative performance of rear facing
child restraint systems on the CMVSS 213 bench and vehicle seats.
Ann Adv Automot Med 2013. 57, 311.
---------------------------------------------------------------------------

    Britax, JPMA, and Graco noted the difficulty to source the ECE R.44
foam. Britax stated that while it did not oppose the use of the ECE
R.44 foam in principal, it strongly recommended that NHTSA survey the
marketplace to better determine the availability of this type of foam
for U.S. CRS manufacturers. Britax stated that the ECE R.44 foam is not
readily available and to require its use for side impact testing may
create a considerable hardship both from a cost and availability
perspective. Britax stated that supplying consistent foam for FMVSS No.
213 standard seat assembly requirements has been a challenge for all
CRS manufacturers who engage in internal sled testing. Britax explained
that it has always been difficult to source cost effective supplies of
foam that have the density, stiffness and qualities necessary for sled
testing. Britax suggested that, since the seat cushion foam stiffness
has minimal effect on dummy responses (as stated by the agency), it may
be a reasonable solution to continue to permit the use of FMVSS No. 213
seat cushion foam. Graco explained that various parties use different
types of foam due to the difficulty of sourcing the foam.
    Britax and Graco also commented on the importance of having
sufficient foam specifications to source the foams. Britax stated that
it would be essential to specify foam density and content. Graco
requested that NHTSA provide clear seat foam drawings, material
definition, indentation load-displacement (ILD) properties and a seat
foam test methodology.
    JPMA commented that all members were concerned with viable
competitive test equipment sourcing and availability and that it
believed a single source and supply with no competition is untenable.
Agency Response
    NHTSA's research program to develop a standard seat cushion with
similar characteristics of seat cushions in more recent vehicle models
resulted in the development of a foam, referred to as the ``NHTSA-
Woodbridge'' \138\ seat cushion foam,\139\ that the agency proposed to
use in the November 2, 2020 NPRM to upgrade the frontal impact seat
assembly. In that NPRM, NHTSA noted that after additional research and
testing,\140\ the agency determined that the ECE R.44 and NPACS seat
foam stiffness were not representative of the U.S. vehicle fleet (in
both quasi-static and dynamic stiffness). Specifically, Figure 5 below
shows that the ECE R.44 and NPACS foams were found to be stiffer than
the vehicle fleet. The FMVSS No. 213 foam, tested on the standard seat
assembly with a cover, is on the low end of the vehicle fleet rear seat
stiffness. The NHTSA-Woodbridge seat cushion shows an average dynamic
stiffness response compared to the vehicle rear seats sample.
---------------------------------------------------------------------------

    \138\ The Woodbridge Group is a supplier of automotive seat
foam, http://www.woodbridgegroup.com.
    \139\ The NHTSA-Woodbridge seat cushion consists of the foam
material covered by the cover used in test procedures of ECE R.44.
The ECE R.44 cover material is a sun shade cloth made of poly-
acrylate fiber with a specific mass of 290 (g/m\2\) and a lengthwise
and breadthwise breaking strength of 120 kg (264.5 pounds) and 80 kg
(176.3 pounds), respectively.
    \140\ Wietholter, K., Louden, A., Sullivan, L., & Burton, R.
(2021, September). Evaluation of seat foams for the FMVSS No. 213
test bench. Washington, DC: National Highway Traffic Safety
Administration.

---------------------------------------------------------------------------

[GRAPHIC] [TIFF OMITTED] TR30JN22.008

    NHTSA is adopting the NHTSA-Woodbridge seat cushion foam in the
SISA because it has characteristics that best represent an average
vehicle rear seat in the United States. In addition, the NHTSA-
Woodbridge seat cushion foam is easier to procure than the ECE R.44
foam proposed for use in the 2014 NPRM. To simplify procurement of the
desired seat cushion foam, NHTSA's FMVSS No. 213 Side Impact Test
Evaluation and Revision report sets forth characteristics of the NHTSA-
Woodbridge seat cushion foam.\141\ Further details of seat cushion
characteristics are available in the drawings that are in the docket
for this final rule. In response to Britax, Graco, and JPMA's concerns
about the ability to source cost-effective seat cushion foam, NHTSA
launched a program to identify foam manufacturers and has found four
sources that can provide the specified foam. These sources are
available in the report, ``Foam Feasibility Study,'' \142\ that is
available in the docket for this final rule.
---------------------------------------------------------------------------

    \141\ Louden & Wietholter (2019).
    \142\ ``Foam Feasibility Study by National Center for
Manufacturing Sciences'' (NHTSA, June 2018). This document is in the
docket for this final rule.
---------------------------------------------------------------------------

    In response to MGA's comment that the seat cover material, foam
insert, and overall assembly for the seat cushions could be harmonized
between FMVSS No. 213 and 213a, the agency has taken steps to keep
FMVSS No. 213a as harmonized as possible with the FMVSS No. 213 frontal
seat assembly proposed on November 2, 2020. This includes the cover
material, foam insert, and overall assembly of the seat cushions. NHTSA
agrees that there are benefits to harmonizing FMVSS No. 213 and 213a to
the extent possible, and that it makes sense that the seat assembly
used to represent vehicle seats in the side crash test would be similar
to the seat used in the frontal test.
    While CU, Dorel, Graco and UPPAbaby considered the ECE R.44 seat
foam appropriate for side impact testing, NHTSA's additional research
shows that the ECE R.44 foam is stiffer than an average vehicle rear
seat. The NHTSA-Woodbridge foam is softer than the ECE R.44 foam and is
a good representation of the average cushion stiffness of rear seats in
the current vehicle fleet. This also accords with Mr. Hauschild and
Graco's suggestion to have a seat foam that is representative of the
current vehicle fleet.
    In the November 2, 2020 NPRM upgrading the FMVSS No. 213 frontal
impact seat assembly, NHTSA proposed the NHTSA-Woodbridge seat cushion
foam thickness of 4.0  0.5 inches (101.6  12.7
mm). JPMA and Graco expressed concern regarding the proposed tolerance
of the seat cushion thickness in their comments to the November 2, 2020
NPRM, noting that the proposed tolerance in the seat cushion thickness
(0.5 inches (12.7 mm)) could result in
increased test variability. JPMA reiterated its concerns regarding the
proposed tolerance in the seat cushion foam thickness in a meeting with
NHTSA on December 15, 2021,\143\ and provided sled test results showing
variability in performance measures when tested with seat foam
thicknesses ranging between 3.67 to 4.42 inches (93.2 to 112.3 mm).
NHTSA agrees with the commenters on this issue and sees merit in
reducing the tolerance of the seat cushion thickness to a level that
would reduce variability in testing, while also ensuring availability
of foam that meets specifications. After reviewing all available
information, NHTSA is specifying a NHTSA-Woodbridge seat cushion foam
thickness of 4.0  0.25 inches (101.6  6.35 mm).
This change is reflected in the drawing package incorporated by
reference by this final rule.
---------------------------------------------------------------------------

    \143\ We submitted a memorandum summarizing this meeting to
Docket No. NHTSA-2014-0012.
---------------------------------------------------------------------------

    Due to the change in seat cushions from the ECE R.44 foam (which is
127 mm (5 inches) thick) to the NHTSA-Woodbridge cushion (which is
101.6 mm (4 inches) thick), NHTSA modified the SISA to account for
changes to the seat cushion height. Using a thinner seat cushion
lowered the position of the installed CRS on the seat assembly with
respect to the door and armrest height, so the agency lowered the
position of the door and armrest by about 25.4 mm (one inch) so that
their relative position with respect to the installed CRS in the seat
assembly are the same as that in the

2014 proposal (which is representative of the current vehicle fleet).
This is discussed further in the section below on the SISA's door and
armrest thickness and stiffness.
ii. Lower Anchorages and Top Tether Anchorages of the CRAS
    FMVSS No. 213 currently requires CRSs to be capable of being
secured to a vehicle seat with the child restraint anchorage system
(CRAS), and to meet the frontal crash requirements of the standard when
using the CRAS. A CRAS consists of two lower anchorages and one upper
tether anchorage. Each lower anchorage includes a rigid round rod or
``bar'' onto which a hook, a jaw-like buckle or other connector can be
snapped. The bars are located at the intersection of the vehicle seat
cushion and seat back. The upper tether anchorage is a ring-like object
to which the upper tether of a CRS can be attached. (FMVSS No. 213 also
requires that CRSs must be capable of being secured to a vehicle seat
using the vehicle's seat belt system.)
    NHTSA proposed that CRSs covered in the proposal, other than belt-
positioning seats, meet the side impact performance requirements when
attached to the SISA with the lower attachments of the CRAS. NHTSA also
proposed that forward-facing CRSs supplied with a top tether may have
that top tether attached during testing if the written instructions
accompanying the CRS instruct owners to attach the top tether when
using the restraint. As discussed further in a section below, NHTSA has
adopted the above provisions in the test procedure for this final
rule.\144\ This section discusses the proposed specifications for the
CRAS lower anchorages and top tether anchorages on the SISA, comments
received, and the final specification of the anchorages.
---------------------------------------------------------------------------

    \144\ NHTSA has also adopted a requirement that CRSs be tested
with a Type 2 seat belt (lap and shoulder belt) with the child
restraint system's top tether attached, if provided.
---------------------------------------------------------------------------

    NHTSA proposed that the SISA be equipped with 2 inches (50.8 mm)
wide CRAS lower anchorages that were symmetrically located on either
side of the centerline of the simulated ``outboard seating position''
of the SISA seat. NHTSA proposed that the top tether anchorage be
located on the lower rear frame of the seat, similar to the typical
location of a tether anchorage in captain's seats in minivans. The
exact locations of the proposed CRAS lower anchorages and tether
anchorages were included in drawings posted to the docket for the NPRM.
Comments Received
    UMTRI commented that the width of the lower anchor bars on the buck
appeared to be 2 inches, rather than the 1-inch minimum required in
FMVSS No. 225, ``Child restraint anchorage systems,'' and most commonly
used by vehicle manufacturers. UMTRI noted that in the NPRM, NHTSA
stated that a European side impact test method was not suitable for
testing U.S. products because it allows the connectors to slide. The
commenter believed use of a 2-inch wide anchor rather than a 1-inch
wide anchor may have the same effect and be unrealistic relative to the
U.S. market.
    MGA provided comments identifying potential interference of the
SISA intruding door with the anchorage locations. First, MGA identified
that because the lower anchor assembly protrudes through the seat
bight, it was found to contact some CRS bases during their testing. In
addition, MGA stated that the lower anchor assembly interferes with
both the corner of the door fixture and the bottom of the seat cushion.
MGA suggested that if the NPRM specifications for lower anchor location
were desirable, the cushion foam design could be adjusted to
accommodate the anchor, or the designed cutout in the seat foam could
be made smaller and still provide clearance for the anchor assembly.
MGA believed that a smaller cutout would provide the benefit of a
larger area for the CRS to sit during the test.
Agency Response
    Modifications to the SISA have resulted in some changes to the
lower anchorages. First, in response to MGA's comment, NHTSA updated
the lower anchor location and cushion design and specifications to
eliminate the lower anchor interference with CRS bases, corner of the
door fixture, and seat foam. NHTSA also eliminated the foam cutouts, as
discussed further below. In making these modifications, NHTSA also made
the SISA lower anchorage locations consistent, as practically possible,
with the lower anchorage locations in the proposed standard seat
assembly of the frontal impact sled test. In addition, NHTSA decreased
the anchorage width to 1.5 inches (38.1 mm). This is wider than those
generally found in vehicles, but is within the 60-mm maximum allowable
anchorage width specified in FMVSS No. 225. Because the standard seat
assembly is used repeatedly and the anchorages will be subjected to a
crash environment repeatedly, the new lower anchorages were made more
robust than the anchorages in a vehicle, and designed in a way that
allows easy replacement when the anchorages are deformed.
    In response to UMTRI, while these wider anchorages may allow some
movement of the CRS on the sliding seat assembly during the impact, the
movement is slight and nowhere comparable to the European sliding
anchors that allow 200-250 mm (7.87-9.84 inches) of movement. NHTSA has
not measured the displacement of the CRS on the seat assembly during
the impact event; however, in the 2014 NPRM the agency compared the
dummy kinematics and injury measures in the side impact sled test to
that in a vehicle side impact test and found them to be similar. NHTSA
believes the effect of this sliding due to the length of the anchorage
is minimal.
Comments Received
    SRN requested that the proposed tether anchor location be further
reviewed because a tether anchor located lower on the back of the seat
has been shown to be less effective in far side impact testing.\145\
SRN argued that using a high tether anchor position on the proposed
SISA would have an additional benefit even if it were not required for
compliance in near side crashes. SRN stated that this would simplify
the process for manufacturers to conduct voluntary center and far-side
impact testing using a SISA configuration that more closely resembles
the real world. Similarly, UMTRI questioned why the top tether location
on the SISA was located on the lower seat back, instead of on a
location representing the rear filler panel, as with the FMVSS No. 213
frontal impact standard seat assembly. UMTRI also argued that top
tether anchorages located on the rear filler panel is more commonly
found in vehicles. MGA commented that the tether placement for FMVSS
No. 213a is located in a position that most closely resembles the floor
of a vehicle, while the tether anchor location for current FMVSS No.
213 is in a location that most closely resembles a top shelf. MGA
stated that while tether placement differs in all vehicle makes and
models, FMVSS No. 213 and 213a should have similar locations for the
tethers.
---------------------------------------------------------------------------

    \145\ Klinich et al. ``Kinematics of the Q3s ATD in a Child
Restraint under Far-Side Impact Loading, Paper #05-0262.
---------------------------------------------------------------------------

Agency Response
    This final rule adopts the proposed location of the tether
anchorage. As discussed above, the SISA tether anchorage is located on
the lower rear

frame of the seat and is similar to the typical location of a tether
anchorage in captains' seats in minivans. The 2012 Vehicle Rear Seat
Study found that 45% of the tether anchors were found on the rear shelf
location, 40% were found on the seat back, 10% were located on the
roof, and 5% in other locations. While a tether anchorage on the rear
shelf was found more frequently in the vehicle survey, the agency
decided to locate it on the seat back for several reasons. First, NHTSA
considered that tether use had no substantive effect on CRS performance
in the near-side impact test, because the simulated door impacts the
CRS before the tether has significant engagement.\146\ Further, a
longer distance to the tether anchorage (as found in a seat back tether
anchorage position compared to one located in the rear shelf) in a
frontal test may result overall in a more stringent test as the tether
may experience more webbing elongations when attached to the seat back
vs. the rear shelf. Also, NHTSA is interested in keeping the frontal
and side impact standard seat assemblies as similar as possible, and
agrees with MGA that the FMVSS No. 213 and 213a seat assemblies have
similar locations for the tethers. Therefore, the agency decided to
keep the tether anchorage locations in a seat back position in both
seat assemblies.
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    \146\ While there may be no effect of tether use and/or tether
anchorage position in a near side impact, use of a tether may
improve the repeatability of the test. Also, there may be some
effect of tether use in center and far-side impact environments,
which would be relevant to researchers conducting center and/or far-
side impact testing. Such testing would likely involve changing the
SISA and door assembly to resemble a center/far-side environment,
and adapting the SISA in such a manner would require substantial
changes to the sliding seat (i.e. making it wider to represent the
center and/or the far-seating positions in a rear seat) and/or to
the door assembly to position the door intrusion at an appropriate
distance for a center/far-side impact environment. Entities engaged
in such modifications can also consider changing the location of the
tether as part of their evaluation.
---------------------------------------------------------------------------

    The lower anchorage locations from the 2012 Vehicle Rear Seat
Survey, the proposed child restraint anchorage locations to the frontal
impact test seat assembly,\147\ and the updated side impact assembly
are shown in Table 16.
---------------------------------------------------------------------------

    \147\ 85 FR 69388, supra.

 Table 16--Lower Anchors and Tether Anchor Locations From (1) the 24 Vehicle Survey, (2) the Proposed FMVSS No.
 213 Frontal Impact Sled Test Standard Seat Assembly, and (3) the Final Side Impact Seat Assembly Configuration
      (All Measurements are in Millimeters From Point A 148 of the Seat Geometry Measuring Fixture (SGMF))
----------------------------------------------------------------------------------------------------------------
                                                                                Final side
                                             Average from vehicle     Proposed frontal test seat     test seat
                                                    survey                  assembly (2020)          assembly
----------------------------------------------------------------------------------------------------------------
Lower Anchors:
    Aft.................................  100  21.......  58........................              60
    Lateral.............................  137  29.......  140.......................             141
    Vertical (-) Below point A..........  -12  24.......  -38.......................             -39
Tether Anchors (Seat Back Position):      ..........................
    Aft.................................  280  88.......  330.......................             324
    Lateral.............................  0  44.........  0.........................               5
    Vertical (-) Below point A..........  140  281......  133.......................             133
----------------------------------------------------------------------------------------------------------------

    UMTRI commented that to allow access to lower anchors, there is a
large gap between the bottom of the seatback foam and the top of the
seat cushion foam on the seat buck. UMTRI explained that when used with
some rear-facing child restraints, the profile of the restraint surface
that rests against the seatback may slip into the gap in an unrealistic
manner. UMTRI added that in the ECE buck, there is space between the
two foam segments, but the seatback foam is angled so there is some
foam in the gap. UMTRI stated that this provides a more realistic
seatback contour than the proposed SISA buck design.
---------------------------------------------------------------------------

    \148\ The 2012 Vehicle Rear Seat Study measured the vehicles'
seat geometry and anchorage locations using a seat geometry
measuring fixture (SGMF). The SGMF consisted of two wood blocks (600
mm x 88 mm x 38 mm) and a 76 mm (3 inches) hinge. To make the rear
seat geometry measurements, the SGMF was positioned on the
centerline of each rear seat position. Point A, which corresponds to
the hinge location of the SGMF, was the reference point for all
measurements.
---------------------------------------------------------------------------

    By way of background, NHTSA designed the side and frontal sled test
seat assemblies taking into consideration the current difficulties to
install and to measure installation tensions (seat belt and lower
anchor). The updated design has proven to allow for easier installation
in the buck and in some cases reduced the difficulty of measuring
installation tension. During extensive side and frontal impact testing
with the updated seat assemblies that have a gap in the seat bight
(between the seat back and seat cushion foam), the agency has not seen
any issues in CRS placement or during testing as mentioned by UMTRI.
Among more than 200 tests conducted on the side impact sled system with
rear-facing and forward-facing CRSs, NHTSA did not experience any
issues with the seat bight gap. Accordingly, this final rule does not
make the requested change.

2. Door Characteristics

i. Beltline Height
    NHTSA proposed a beltline (window sill) height of 500 mm (19.6
inches) for the SISA, based on a survey of 24 vehicles. Although the
proposed beltline height (500 mm) was slightly higher than the average
(494 mm) and median (489 mm) beltline heights of the surveyed vehicles,
HIC values were generally higher at the higher beltline height. NHTSA
proposed the higher value to ensure that the side impact test was
sufficiently stringent to account for vehicle beltlines higher than the
average value. Child restraint systems meeting the HIC15 requirement
when tested against the 500 mm beltline will likely provide sufficient
crash protection in vehicles with a lower beltline, but the opposite
may not be valid. CRSs tested against a lower belt line might not
adequately protect children in vehicles with the higher (500 mm)
beltline design.
Comment Received
    CU stated that the NPRM's fleet study of seats seemed to have been
conducted at the 479 mm (18.8 inches) height and that even at that
lower height, 7 of 12 forward-facing CRSs had HIC15 values in excess of
the proposed 570 limit. CU stated, ``Though the five seats with the
lower HIC15 had a notable margin between their values and the 570
limit, it may be an expectation that at the higher beltline height more
CRSs would approach or exceed that limit.'' CU added that the higher
beltline may also

produce a larger differential when compared to the performance of seats
in the sled/vehicle test comparison.
Agency Response
    Contrary to CU's understanding, our fleet testing of forward-facing
CRSs discussed in the NPRM \149\ were performed at the higher beltline
height (500 mm or 19.6 inches), not the lower beltline height (479 mm
or 18.8 inches) that was first used during development. Tested against
the 500 mm beltline height, the fleet test results of forward-facing
CRSs with the Q3s dummy showed that 7 out of 12 CRSs exceeded HIC15
injury limits and that 3 out 12 tests resulted in chest deflection
exceeding the proposed limit (23 mm). Fleet tests of rear-facing CRSs
tested with the Q3s showed that 3 out of 5 exceeded HIC15 injury limits
and 2 out of 5 exceed chest deflection injury limits. For the 5 rear-
facing CRSs tested, the results of the fleet tests showed that the Q3s
measured HIC15 greater than 570 in 3 of the 5 rear-facing CRSs tested,
and chest deflection greater than 23 mm in 2 of the 5 tests. The Q3s
measured both HIC15 greater than 570 and chest deflection greater than
23 mm in 1 of the 5 rear-facing CRSs tested.
---------------------------------------------------------------------------

    \149\ Id. at 4593.
---------------------------------------------------------------------------

    Tests with the 12-month-old CRABI dummy in rear-facing CRSs showed
that the different beltline heights did not affect dummy responses.
NHTSA believes this was due to the fact that most rear-facing CRSs
designed for smaller children position the head lower (mostly below the
beltline) and therefore the increased height (at 500 mm or 19.6 inches)
did not affect the outcome. For this reason, fleet testing with the 12-
month-old CRABI dummy in rear-facing CRSs did include tests done at 500
mm and at 479 mm. Results of rear-facing CRSs using the 12-month-old
CRABI dummy showed that only 1 out of 12 models had head to door
contact. NHTSA believes the tests selected for the fleet testing and
cost benefit analysis in the NPRM were appropriate and accounted for
the increased stringency of the higher beltline. Accordingly, NHTSA is
not making any changes to the SISA beltline height from that proposed
in the NPRM.
ii. Door and Armrest Thickness and Stiffness
    NHTSA proposed that the door panel/armrest configuration for the
SISA would consist of 51 mm (2 inches) ``average'' stiffness foam
padding (Dow Ethafoam 220) on the door and a 64 mm (2.5 inches)
``stiff'' foam (United Foam #4) for the armrest. NHTSA determined that
this door panel/armrest configuration had similar characteristics to
those observed in Free Motion Headform (FMH) impact testing of eight
vehicle doors. Those tests are described in detail in NHTSA's 2013
report, Child Restraint Side Impact Test Procedure Development.\150\
The proposed armrest thickness also fell within the range of vehicle
armrests measured in the 2012 Vehicle Rear Seat Study.
---------------------------------------------------------------------------

    \150\ Sullivan, L., Louden, A., Echemendia, C., ``Child
Restraint Side Impact Test Procedure Development'' (December 2013),
available at Docket No. NHTSA-2014-0012-0002 [hereinafter Sullivan
et al. (2013)].
---------------------------------------------------------------------------

    In addition to the representativeness of that door panel/armrest
configuration of average rear seat characteristics, NHTSA stated that
the proposed door padding (Ethafoam 220) was of lower cost compared to
the other foams, was relatively easy to obtain commercially, and was
relatively fungible, in that other materials with similar physical
properties could easily be used in its place. NHTSA also cited to
results of its sensitivity analyses that showed door stiffness had
little effect on dummy performance.\151\
---------------------------------------------------------------------------

    \151\ Sullivan et al. (2011).
---------------------------------------------------------------------------

Discussion of Comments
    CU commented that the FMVSS No. 201 test procedure that NHTSA used
as a basis for determining average door and armrest stiffness was also
utilized by CU in its revised CRS testing protocol, and therefore CU
supported that aspect of the NPRM. ARCCA commented that while it did
not have data to confirm or deny the appropriateness of the door/
armrest configuration, it was unaware of any rear door configuration
with the level of padding specified for the proposed SISA. ARCCA stated
that, accordingly, the HIC values acquired from head to door impact
would likely underpredict the severity of the head impact.
    NHTSA disagrees with ARCCA. The stiffness of the simulated door in
the SISA is representative of the stiffness found in vehicles, which
NHTSA determined using the FMH testing described above. The stiffness
of the 51 mm thick door padding includes the combined stiffness of the
door assembly (inner and outer panel of the door) and the interior door
padding. The relevant factor for the test is door stiffness and not the
thickness of the door padding. Details of the development of the door
characteristics can be found in the ``Child Restraint Side Impact Test
Procedure Development'' technical report.\152\
---------------------------------------------------------------------------

    \152\ Sullivan et al. (2013).
---------------------------------------------------------------------------

    Both JPMA and MGA noted a discrepancy between the NPRM
specification for door foam thickness (51 mm) and the drawing package
specifications (55 mm). JPMA stated that this difference in foam
thickness is significant because ``the NPRM includes set-up distances
from the face of the door panel to the face of honeycomb material and
from the face of the honeycomb material to the centerline of the
sliding seat [sic].'' JPMA explained that the thickness of the foam is
thus an important part of these set-up relationships and needs to be
the same in the final rule and the drawing package to help ensure
consistent test results between test facilities. MGA stated that it
believed the error was on the part of the drawings, as 55 mm (2.2
inches) foam is not commonly available.
    NHTSA agrees with MGA that there are inconsistencies in the door
foam thickness specification between the NPRM and the drawing package.
The door foam was procured as a 2-inch nominal thickness foam plank.
According to the foam manufacturer's terminology,\153\ an X-inch
nominal foam thickness means that the foam plank is gauged at a desired
thickness of X + \1/4\ inches. Therefore, a 2-inch nominal thickness
foam plank has a thickness of 57 mm (2.25 inches). Accordingly, NHTSA
has changed the door foam thickness measurements in Drawing 2921-501
from 55 mm (2.2 inches) to 57 mm (2.25 inches). The specified foam,
with a thickness of 57 mm (corresponding to a 2-inch nominal foam
thickness) is commonly available. Graco made several recommendations
relating to the door foam's characteristics over time and extended use.
The commenter recommended replacement of the door foam only after
significant structural damage. It recommended that NHTSA provide a
standardized method for measuring the compression properties of the
door foam. Graco provided developmental test results showing that
maximum HIC15 and chest deflection results occur at the time of contact
with the door structure.\154\ Graco suggested that NHTSA should confirm
that performance after extended use does not change results. Graco
explained that currently the foam types are described as ``Soft''
(United Foam # 2), ``average'' (Dow Ethafoam 220), and ``stiff''
(United Foam # 4) foam. Graco suggested that, if these descriptions can
also include a method for confirming compression

properties after extended use, crash test facilities can confirm that
injury metric results are not affected by changes in foam properties.
---------------------------------------------------------------------------

    \153\ Link to foam manufacturer's terminology: https://www.customfoaminc.com/CustomFoamProductsSpecSheet.pdf.
    \154\ NHTSA-2014-0012-0042, at pg. 9.
---------------------------------------------------------------------------

    MGA reported that they did not replace the door and armrest foam
between tests (approximately 40 tests). MGA used a single piece for the
door and two pieces for the armrest attached with spray adhesive. MGA
reported that the foam assembly did not show any physical degradation
nor change in thickness during their test series.
    During NHTSA's research testing, the door foam was reused for 2 to
3 tests as no extensive damage was seen during initial tests, while the
armrest foams were used only once as they presented indentations from
the impact of a single test. Since there is no method to retest for the
compression properties of the door and armrest foams after use, NHTSA
frequently replaces these foams.\155\ How frequently NHTSA will replace
these foams in its compliance testing program will be indicated in
NHTSA's compliance test procedure for FMVSS No. 213a that will be
included on NHTSA's website.\156\
---------------------------------------------------------------------------

    \155\ The research test procedure developed at VRTC specifies
use of a new foam for each test. This test procedure is in the
following report in the docket of this final rule: Louden, A., &
Wietholter, K. (March 2022). FMVSS No. 213 side impact test
evaluation and revision (Report No. DOT HS 812 791). Washington, DC:
National Highway Traffic Safety Administration (hereinafter Louden &
Wietholter (20)).
    \156\ The NHTSA Office of Vehicle Safety Compliance FMVSS No.