c.  New Dummies

1.  Post-NPRM Test Program

As part of the test program conducted for NHTSA at the Patuxent River (PAX) test center, PAX conducted a series of dynamic sled tests to evaluate identical child restraints on the revised test seat assembly using both the Hybrid II and the Hybrid III 3-and 6-year-old dummies.  All of these tests were conducted with the restraints attached to the test seat assembly with the lap belt only, as would be done in a compliance test. Similar comparison tests were conducted with the Hybrid II 9-month-old and the CRABI 12-month-old dummy, but as the 9-month-old dummy is uninstrumented, little comparative information was gleaned from these tests. Accordingly, the data from the latter tests are not provided.

i.          Tests With The 3-Year-Old Dummies

The following Table 6 illustrates the injury criteria measurements for the test series using the Hybrid II and Hybrid III 3-year-old dummies:

TABLE 6:  TESTS WITH THE HYBRID II AND HYBRID III 3-YEAR-OLDS

The Cosco Touriva and the Century Accel are both forward-facing convertible child restraints, and the Century Breverra and the Cosco High Back Booster are forward-facing hybrid boosters. All were tested with the dummy in the restraint’s internal harness system.

The results from this series of testing appear to be mixed. Three of four tests showed a marked decrease in measured HIC values when testing with the Hybrid III dummy as compared to the Hybrid II dummy, while the fourth test in the series resulted in a significant increase (446.4 to 704.9) in HIC values. Similar results are seen when looking at chest acceleration and head and knee excursions. The varied results can be attributable in part to the very limited sample size of child restraints tested. No repeatability tests were performed. All injury numbers were well within the current limits prescribed in FMVSS No. 213.

ii.        Tests With The 6-Year-Old Dummies

A similar series of tests was conducted with the Hybrid II and Hybrid III 6-year-old dummies in both backless and high back belt-positioning booster seats on the revised test seat assembly. As was the case in tests with the 3-year-old dummies, the test results for the 6-year-old dummies show considerable fluctuation and no clear trends.

The following Table 7 outlines the results of these tests:

TABLE 7:  TESTS WITH THE HYBRID II AND HYBRID III 6-YEAR-OLDS

The original test matrix called for testing each restraint with both the Hybrid II and the Hybrid III 6-year-olds to facilitate a direct comparison between the two dummies, as was done for the other dummies. However, during the conduct of the sled tests at PAX, the Cosco Grand Explorer was instead inadvertently tested twice with the Hybrid II 6-year-old, and the Evenflo Right Fit was tested twice with the Hybrid III 6-year-old.

NHTSA acknowledges that this makes a direct comparison between the two dummies in the same restraint impossible. However, unlike rear-facing infant seats and forward-facing toddler seats, there is very little difference in design characteristics between the two backless booster seats in question that would influence the dynamic response of the dummies in a sled test. As such, NHTSA has included the data for information.

Further, it is noted that VRTC conducted a study comparing the performance between the Hybrid II and the Hybrid III child dummy families in support of the NPRM for this final rule. (See Docket NHTSA-2002-11707-1; report dated April 12, 2002.)  The report concluded in part that sled test results generally show fairly consistent dummy performance with the Hybrid II and Hybrid III child dummies.

2.  Commenters Generally Supportive

Commenters generally supported using the CRABI 12-month-old and the Hybrid III 3-year-old dummies in Standard No. 213 compliance tests, in place of the TNO 9-month and the Hybrid II 3-year-old dummies now used by the agency. There was support for the use of the Hybrid III 6-year-old dummy in compliance tests, with the exception of a few commenters (discussed below). There was general concern about the need for and capabilities of the weighted Hybrid III 6-year-old dummy.

i.         Hybrid III 6-Year-Old Dummy

Several commenters expressed concern about the biofidelity of the unweighted Hybrid III (HIII) 6-year-old dummy’s neck and hips and the suitability of the dummy for use in testing child restraints. TraumaLink stated that, based on a sled test program it conducted at a test lab, they had "significant concerns" regarding the performance of the dummy. "The tests revealed extremely large neck elongation unlikely to be seen in real children in real crashes and resulted in high calculated injury values. These results suggest a pattern of injuries that we do not see in our real world experience." 

SafetyBeltSafe referred to the tests performed by TraumaLink to conclude that "We do not now believe that the HIII 6-year-old dummy is an appropriate test device to simulate a restrained child" because of "unrealistic stretching and bending of this dummy’s neck while tightly restrained by a lap-shoulder belt in a booster. The result was that the dummy’s face directly contacted the chest, generating an unrealistic and unacceptably high HIC."  SafetyBeltSafe also stated that test data from NHTSA’s Vehicle Research and Test Center indicated that tests with the dummy generated "[head] excursion increases of from 2.1 to 4.5 inches in a booster with lap-shoulder belt. The likely reason for this is that the neck is not a true Hybrid III type neck, as it lacks the metal disks needed to limit its bending."  The commenter was also concerned about the dummy’s "permanently flexed hips, which, unlike the new 10-year-old design, do not allow a slouched position and may inhibit submarining in non-optimal booster designs." 

Ford Motor Company likewise stated that the Hybrid III dummies are much more likely to experience head-to-knee contacts than Hybrid II dummies, because of the more flexible ribs and neck of the HIII dummies. Further, Ford said that a 1984 study (Culver et al.) showed that adult HIII dummy HIC readings were about twice those recorded in dummy head to cadaver knee impacts. Further, Ford stated that because the HIII 6-year-old dummy does not have the metal plates that segment and limit bending of the necks of the HIII adult dummies, the HIII 6-year-old dummy may be more likely to experience head-to-leg contacts than "the three-year-old."  Ford asked in its comment how the agency would treat head acceleration spikes that could be caused by head-to-knee contacts. The commenter also suggested that load cells be used on the ASIS of the pelvis of the 6-year-old dummy to evaluate the tendency to submarine under the lap belt during testing of booster seats, because, Ford stated without elaborating, the current limit on knee excursion is not an effective way to limit submarining in tests of belt-positioning boosters.

NHTSA disagrees with the commenters that the HIII 6-year-old dummy should not be used in FMVSS No. 213 testing. The neck of the HIII 6-year-old is currently performing within the specifications established by the Hybrid III Dummy Family Task Force of the Society of Automotive Engineers (SAE). The agency is not aware of specific test information and/or data substantiating the claims of the commenters that the dummy is an unsuitable test device for FMVSS No. 213 testing.

When the dummy was incorporated into the regulation on anthropomorphic test devices, 49 CFR Part 572, the agency made the following determinations (65 FR 2059) about the dummy :

Based on NHTSA's use of the H-III6C 6-year-old dummy in calibration tests and in frontal impact tests involving restraints such as air bags and belts, we have concluded that this dummy is suitable for both research and compliance safety assessments. The dummy is not only considerably more biofidelic than its predecessor, the Part 572 Subpart I 6-year-old dummy, but it also has considerably more extensive instrumentation to measure impact responses such as forces, accelerations, moments, and deflections in conducting tests to evaluate vehicle occupant protection systems.

The agency continues to believe that the performance of child restraint systems will be more thoroughly and precisely assessed by use of the HIII dummy because of the dummy’s enhanced biofidelity and extensive instrumentation. With regard to concerns about the dummy’s neck, it should be noted that the Hybrid II dummy currently in use also does not have the metal disks. Since the Hybrid III is more biomechanically based, we continue to believe that it provides a more humanlike response than the Hybrid II version of the dummy.

Sled tests have shown the HIII 6-year-old to be a suitable replacement for the existing HII 6-year-old in FMVSS No. 213 compliance tests. None of the sled testing conducted with the HIII 6-year-old dummy at VRTC or PAX in support of the TREAD Act has indicated that head-to-chest or head-to-knee impacts is an issue. Such impacts are not typical. [11]   NHTSA believes that if head-to-knee contact occurs, there are likely design concerns with respect to the particular child restraint that should be addressed to eliminate such contact. We also believe it would be very difficult, if not impossible, to establish an objective means to determine if, and if so to what extent, head-to-knee contact influenced HIC measurement in FMVSS No. 213 compliance testing. Consequently, head acceleration spikes caused by head-to-knee contacts will be included in the HIC computation. Further, the agency continues to believe that the HIII dummy is needed to better assess the injury mechanisms to children.

The agency is not entirely convinced that neck elongation is not occurring to children in real crashes. We believe it possible that neck injury may sometimes not be diagnosed even though it occurs. Since a child’s neck is not fully developed, detection of injuries is more difficult and injuries could manifest in later years. Also, for fatal injuries, there is often a reluctance to conduct autopsies in deference to family sensitivity. Consequently, the cause of death may be listed as massive head injury, while injury to the neck may have also occurred.

The agency is continuing to conduct research to establish better neck injury response and injury criteria for children. Research may show the presence of neck injury and a possible need for a neck injury criterion in FMVSS No. 213. If that occurs, a test dummy incorporated into the standard that offers improved biofidelity and neck instrumentation would prove useful. Because we believe that the current neck on the HIII 6-year-old dummy provides improved biofidelity over the current dummy and is suitable for compliance purposes, this final rule adopts the dummy into FMVSS No. 213 as proposed.

ii.         Weighted 6-Year-Old Dummy

A majority of commenters raised concerns with the biofidelity of the weighted 6-year-old-dummy, which is intended to model a 50^th percentile 8-year-old child. IIHS and NTSB commented on the importance of height in measuring seat belt fit and injury criteria, particularly head excursion. Both determined that the weighted dummy failed to accurately represent the height of booster occupants. NTSB stated that the addition of weight to the dummy’s spine and pelvis was not representative of weight distribution in an actual child. Ford expressed concern that the weighting of the 6-year-old dummy could result in inaccurate output of the injury criteria. Ford expected the weighted dummy to show abnormally high chest deflection and abnormally low chest acceleration, and higher head excursion. Ford was also concerned that the low relative mass of the lower extremities could reduce knee excursion compared to a more biofidelic dummy. Ford stated that adding mass to the spine and lengthening the lumbar spine might result in the weighted dummy not submarining under conditions that would cause a more biofidelic dummy to submarine. Public Citizen, Graco, and the Alliance commented that the weighted dummy would not perform the same as the 10-year-old dummy which NHTSA has been developing and which was referenced in P.L. 107-318 (Dec. 4, 2002; 116 Stat. 2772)("Anton’s Law"). [12]  

IIHS, ACTS, Public Citizen, the Alliance, and GM stated that the lack of biofidelity should preclude the use of the weighted dummy. Many commenters urged the agency to develop the 10-year-old dummy as an alternative. Public Citizen urged the agency to move ahead with regulations in anticipation of the 10-year-old dummy’s future availability. NTSB suggested using the European 10-year-old dummy (P-series) as an interim measure. While acknowledging the existence of problems with the P-series, NTSB stated that European dummy would better represent height and seat belt fit.  

While raising concerns with biofidelity, a number of commenters agreed that, if necessary, the weighted 6-year-old dummy could be used in a limited capacity to test the structural integrity of child restraints until such time as the Hybrid III 10-year-old dummy became available. Evenflo also supported using the weighted dummy to measure head excursion.

The agency agrees that the Hybrid III 10-year-old dummy, envisioned by Anton’s Law, represents the long-term solution to the issue of testing booster seats certified for higher weights. Development of the Hybrid III 10-year-old dummy is proceeding as quickly as possible, but this dummy is not currently ready for use in compliance tests. The agency is currently testing the Hybrid III 10-year-old dummy to determine its suitability for FMVSS No. 213 compliance testing. A notice proposing to incorporate this dummy into Part 572 for use in compliance testing is expected to be published in early 2004.

Despite limited results showing a general correlation between the testing performance of the weighted 6-year-old dummy and the Hybrid III 6-year-old dummy, the agency is persuaded by the comments that the weighted dummy should not be used for testing with full instrumentation. The weighted dummy would not perform the same as the 10-year-old dummy in development and it may not accurately represent an 8-year-old child. IIHS stated that the weighted dummy is too short to represent the tallest occupants for whom boosters are recommended, noting that "[s]itting height is an important factor in testing booster seats because a poorly designed booster may permit too much head excursion for taller occupants. Weight is, at most, a secondary issue for the restraints because the vehicle belts, which are not subject to testing under this standard, restrain the inertia of booster seat occupants."

While the 0.7-inch increase in sitting height achieved through the addition of weights to the Hybrid III 6-year-old dummy is comparable to that of a 50^th percentile 8-year-old child, the overall weight and height, and consequently the weight distribution, are not. The 50^th percentile 8-year-old child is 50.5 inches tall, as compared to the 50^th percentile 6-year-old child which is 45.5 inches tall. The weight added to the 6-year-old dummy is not distributed as it would normally be on a 50^th percentile 8-year-old, making injury measurements suspect.   

The agency agrees that the kinematics of the weighted 6-year-old dummy may not be representative of the older child that it attempts to model and it could potentially interact with the belt system differently than a dummy developed to represent an 8-year-old child. Therefore, the weighted dummy will be used only as a means of ballast to evaluate the structural integrity of the tested child restraint. While the weighted dummy will not be instrumented to determine compliance, it will be instrumented to collect data for use in research.

Anton’s Law [13] directs the agency to initiate a rulemaking proceeding to establish performance requirements for child restraints, including booster seats, for the restraint of children weighing more than 50 lb. Through use of the weighted 6-year-old dummy, the structural integrity of a CRS recommended for children between 50 and 65 lb can be tested. NHTSA recommends children to be placed in booster seats until they are 8-years old, or 57 inches tall. The weight of a 50^th percentile 8-year-old male is approximately 57 lb. The weight of a 50^th percentile 8-year, 9 month-old male is approximately 62 lb. Use of the 62 lb weighted dummy as ballast ensures that booster seats certified up to 65 lb will not structurally fail in a crash.

While several commenters suggested using alternative dummies as an interim measure, none of the suggested alternatives are appropriate even for use as ballast. NTSB recommended using the European P-series 10-year-old dummy in a limited capacity to provide a better means of evaluating proper seat belt fit and to enhance efforts to enact booster seat laws in the states. NHTSA is not confident in the ability of the P-series dummy to uniformly load the restraint system in a manner necessary for the evaluation of the booster seat, even structurally. The P-series dummy is designed with too many degrees of freedom, and its interaction with a restraint system would be inconsistent.

AAP suggested using the Hybrid III 5^th percentile female to test child restraints to allow regulation up to 80 lb in advance of the availability of the Hybrid III 10-year-old dummy. The weight of the Hybrid III 5^th percentile female dummy is 108 lb, 28 lb heavier than the maximum weight of a child that the child restraint would be certified for in compliance testing. The heavier weight of the 5^th percentile female dummy would not offer an accurate representation of an 8-year-old or even 10-year-old child.

3.  Specific Issues Relating To The Use Of The New Dummies In Standard No. 213

i.         Seat Back Height Requirement

S5.2.1.1 specifies that each child restraint system shall provide head restraint by means of a continuous seat back. Subsection (a) of S5.2.1.1 specifies that for child restraints recommended for use by children weighing less than 20 lb, the height of the seat back must be not less than 18 inches. If a restraint were recommended for children weighing 20 to 40 lb, the seat back height must be not less than 20 inches.

Some rear-facing infant car seat/carriers, which are designed with a handle for toting the infant outside of the vehicle, are recommended for use with infants weighing only up to 20 lb. Under current S5.2.1.1, these restraints (recommended for children up to 20 lb) must have a seat back of a height of not less than 18 inches. This final rule amends S5.2.1.1 to require these restraints to have a seat back height of not less than 20 inches.

The agency proposed to use the CRABI dummy in place of the 9-month-old dummy in all tests in which the latter dummy is used, including tests of rear-facing infant car seat/carriers. Thus, it was proposed that the CRABI (at 22 lb) would be used to test car seat/carriers. Comments were requested on the appropriateness of using the CRABI dummy to test infant car seat/carriers recommended for children up to 20 lb, when the 22-lb dummy is heavier than the children recommended for the restraints. Comments were requested on whether all infant car seat/carriers have back supports that are high enough to support the CRABI.

No commenter opposed the use of the CRABI in place of the 9-month old dummy, but some issues were raised about possible effects of using the dummy to test infant seats. Graco suggested that S5.2.1.1 could be deleted, for lack of a safety need, if Standard No. 213 were amended to specify use of the CRABI dummy to assess the ability of a rear-facing restraint to limit the rearward excursion of the dummy in Standard No. 213’s dynamic test (S5.1.3.2). [14]   Evenflo stated that several infant-only restraints do not have backs high enough to support the CRABI 12-month-old dummy. The commenter suggested that replacement of the 9-month-old dummy by the CRABI in 4 years would help minimize the financial impact to child restraint manufacturers.

In response to Graco, NHTSA agrees that S5.2.1.1 and S5.1.3.2 both provide protection to a rear-facing child in a frontal impact by limiting occupant excursion outside of the confines of the restraint system. However, the agency is unable to conclude that the two requirements serve the same safety need for rear-facing restraints. S5.2.1.1 specifies seat back height and width requirements and also limits how far rearward the test dummy’s head may rotate during dynamic testing. These requirements may provide protection in dynamic conditions other than that replicated by the Standard No. 213 sled test. A child restraint might be able to meet S5.1.3.2 with a seat back that is lower or narrower than that specified by S5.2.1.1. Deleting S5.2.1.1’s requirements for rear-facing restraints could reduce some of the current protections afforded by child restraints. Thus, the agency declines to delete S5.2.1.1.  

At the same time, however, the agency has concluded that with the incorporation of the CRABI dummy into the standard, amendments to S5.2.1.1 are in order. Information indicates that infants should be positioned rear-facing until at least 12-months old, until such time their neck and muscular structure are developed to more adequately support their head. If rear-facing infant seats were recommended for use with an infant until the infant weighs 22 lb, there is a greater likelihood that parents will keep their infants in the rear-facing restraint until the infant reaches or is closer to reaching 12 months of age than if the restraint were only recommended for infants up to 20 lb. (The agency believes that many infants are positioned forward-facing in a toddler restraint after being transitioned out of a rear-facing car seat/carrier, and that many of these infants are not developmentally ready to be forward-facing in the vehicle.)

The agency is amending S5.2.1.1(a) to encourage the production of rear-facing infant car seat/carriers that are recommended for use by infants up to 12 months in age. The agency is amending the table in S5.2.1.1(a) such that infant car seat/carriers must have a minimum seat back height of 20 inches. [15]   The effect of this is to require all rear-facing infant restraints to be large enough for an average 12-month-old. As a practical matter, this is not a drastic change. Seventy-five percent of the infant-only seats that have been evaluated in the agency’s ease-of-use ratings program were certified for children weighing up to 22 lb and thus already are manufactured with 20-inch seat backs.

This final rule does not require manufacturers to recommend on the labels accompanying infant restraints that the restraints are recommended for infants up to 22 lb, but provides the incentive for them to do so. Because the 22-lb CRABI will be the test instrument used in compliance tests of the infant seats, and because under S5.2.1.1(a) the infant seats must have a minimum seat back of 20 inches, the agency believes that manufacturers will certify most if not all infant restraints to 22 lb.

The agency is providing for a 2-year leadtime for this change. Evenflo stated that several models of infant-only restraints do not have backs high enough to support the CRABI 12-month-old dummy and will thus have to be redesigned. Evenflo suggested that replacement of the 9-month-old dummy by the CRABI in 4 years would help minimize the financial impact to child restraint manufacturers. JPMA suggested a 3 year leadtime. NHTSA declines to provide such long leadtimes suggested by Evenflo and JPMA because there could be safety benefits associated with keeping more infants rear-facing until they are at least 12-months old, which could result from the change to the CRABI and to S5.2.1.1 of Standard No. 213.  The short deadlines of the TREAD Act also indicate Congress’s interest in having the standard be upgraded as quickly as possible. The 2-year leadtime NHTSA is providing balances the safety benefits with the need for some child restraint manufacturers to modify some of their seats.

ii.         Padding Requirement

The agency asked for comment on deleting S5.2.3, which specifies a padding requirement for child restraints used by children weighing less than 22 lb. The agency had specified the requirement (whose thickness and static compression specifications are compliance-tested statically) because there was no instrumented infant test dummy available at the time (1979) the requirement was adopted. The agency’s goal was to establish dynamic test requirements for infant restraints, so that the total energy absorption capability of the padding and underlying structure could be measured. (44 FR 72131, 72135). Graco and Xportation supported deleting S5.2.3. Since today’s final rule incorporates use of the instrumented CRABI 12-month-old dummy for use in testing restraints recommended for children under 22 lb, we are deleting S5.2.3, as proposed.

4.        Leadtime

The agency proposed in the NPRM that manufacturers be provided two years of leadtime, after publication of a final rule, before specifying the use of the CRABI and Hybrid III dummies in compliance tests. The NPRM proposed using the weighted 6-year-old dummy in compliance tests 180 days after publication of a final rule.

JPMA supported the addition of the new dummies to the standard, provided that the agency gives "a phase in of at least three years from the issuance of the final rule…to avoid costly recertification requirements for existing seats, and to avoid the possible elimination of some current seats from the marketplace."  JPMA stated that because of dimensional differences between the proposed CRABI 12-month-old and the 9-month-old dummy currently used to test infant-only child restraints, the commenter believed that the use of the CRABI dummy will likely result in the elimination of current infant-only child restraints. JPMA stated that "millions of dollars of tooling and development testing will be rendered worthless" by incorporating the new dummies and that "[m]anufacturers should be given a longer lead time before having to endure the several financial consequences of these changes." [16]   Evenflo commented that the agency "must recognize that the use of the new dummies will have a significant affect [sic] on manufacturers’ test costs, which will ultimately be reflected in the price of child restraints."

The agency is providing for a 2-year leadtime for the changeover to the new dummies. As explained above, the agency believes there are safety benefits associated with keeping more infants rear-facing until they are at least 12-months old, which could result from the change to the CRABI and to S5.2.1.1 of Standard No. 213. At the same time, the two year leadtime is provided to lessen the cost impacts of the rule on manufacturers’ testing costs (retesting current child restraints on the new seat assembly using the new dummies, and at test speeds closer to 30 mph) and possible retooling costs.

NHTSA believes there also are safety benefits to testing the structural integrity of child restraints recommended for children weighing from 50 to 65 lb. However, an effective date short of approximately two years is not provided for use of the weighted dummy because the rulemaking incorporating the dummy into 49 CFR Part 572 is not yet completed. The NPRM was published May 7, 2003; 68 FR 24417. The rulemaking should be completed with sufficient time to allow manufacturers to certify their restraints to Standard No. 213 by the two-year compliance date.