d.  Application of the Standard

Most commenters supported increasing the weight limit in the definition of "child restraint system" above the current 50 lb. The only commenter opposed to any increase was the Automotive Coalition for Traffic Safety, because of concern with the weighted 6-year-old dummy. Of those supporting an increase, a majority supported increasing the weight to 65 lb based on the use of the weighted 6-year-old dummy, with future amendments increasing the weight to 80 lb upon the introduction of the 10-year-old dummy. Advocates stated that it would support increasing the limit to 65 lb upon showing that the weighted 6-year-old dummy (62 lb) is sufficient to assess child restraint use with children weighing up to 65 lb. Graco suggested that the agency should defer increasing the limit to the time the 10-year-old dummy is available.   

Several commenters did not support an intermediate level of 65 lb and preferred amending the standard now to specify the application to restraints recommended for children up to 80 lb. Ms. Bidez supported incorporating the 10-year-old dummy in its current form and amending the weight limit to reflect the 80 lb weight of the 10-year-old dummy. AAP recommended using the 5^th percentile female to allow regulation up to 80 lb in advance of the 10-year-old dummy. E-Z-On believed that the limit should be extended to 80 lb, and that costs to vehicle and child restraint manufacturers to provide stronger anchorages and hardware would be minimal.

The agency agrees with commenters in that the weight limit in the definition of "child restraint system" should be increased above 50 lb. While the weighted 6-year-old dummy injury measurement reliability may not be sufficient for compliance testing, the dummy is suitable for testing the structural integrity of child restraints up to 65 lb. Use of the weighted dummy provides an interim weight limit in advance of the Hybrid III 10-year-old dummy. The agency is confident in the ability of the 62-lb-weighted dummy to test restraints certified up to 65 lb. There will be only a 3-lb difference between the weighted dummy and the maximum certification weight. The Hybrid II 3 year-old, weighing 33 lb, has proven efficient at testing child restraint systems certified with a maximum weight of 40 lb.

However, the weighted 6-year-old dummy is not sufficient to assess the dynamic performance of a child restraint in restraining an 80-lb child, and as stated above, use of an alternative dummy to allow increasing the limit to 80 lb is not appropriate. The agency is not confident in the ability of the European P-series 10-year-old dummy to uniformly load the restraint, and the Hybrid III 5^th percentile female is 35 percent heavier than the suggested maximum weight of 80 lb.

For the aforementioned reasons, NHTSA is increasing the reference to the weight limit in the definition of "child restraint system" from 50 lb to 65 lb. This amendment, effective in 180 days, affects primarily manufacturers of child restraints recommended for older children, i.e., booster seat and harness manufacturers. The agency does not anticipate that manufacturers will have to redesign their restraints to certify compliance using the weighted 6-year-old dummy. However, the rulemaking to incorporate the weighted 6-year-old dummy into Part 572 is not complete, so the agency is specifying that compliance testing with the weighted dummy will not begin for two years. Manufacturers are permitted the option of voluntarily using the weighted dummy prior to the mandatory compliance date.  

Several comments were submitted on whether manufacturers should be prohibited from recommending their seats for children of weights higher than the heaviest dummy used to test the restraint. Consumer Union stated that the agency should limit manufacturers’ ability to advertise child restraint weight maximums only to the weight of the heaviest dummy used for its certification testing. Alternatively , Consumer Union stated that the agency should develop dummies that are at the maximum weight advertised for the restraint, or require the addition of ballast weights to existing test dummies.

In contrast, TraumaLink believed that manufacturers should be permitted to recommend child restraints at weights above that of the heaviest dummy used to test the restraint. TraumaLink stated that there was no field data to indicate a problem with convertible restraints (typically recommended for children up to 40 lb) which have been tested with a 33 lb dummy (the Hybrid II 3-year-old). Limiting the regulation based on the heaviest dummy, TraumaLink continued, would place artificial limits on the protections afforded children. Similarly, AAP opposed limiting a manufacturer’s ability to recommend a child restraint for a weight above that of the heaviest dummy used to test the restraint. AAP stated that such a restriction could mislead parents into thinking that children should use seat belts once the child is heavier than 62 lb, when in fact, most children do not fit seat belts until a much heavier weight.

In a rulemaking amending FMVSS No. 213 to incorporate several test dummies into the standard (61 FR 30827; June 18, 1996), NHTSA responded to Consumer’s Union (CU) belief, expressed during that rulemaking, that restraints (e.g., convertible child seats) should not be permitted to be recommended for children weighing more than the largest test dummy used to test the restraint (e.g., 33 lb). The agency determined that such an approach was unnecessarily restrictive, given that there has been no showing that the wider array of dummies incorporated into Standard No. 213 by that rulemaking were insufficient surrogates for the children for whom the restraints are recommended. The agency also believed that CU’s suggestion could have unintended safety consequences, because it would have the effect of forcing young children out of child restraints specifically designed for them (typically 20 to 40 lb) and into restraints that may not be appropriate for their size, i.e., booster seats for a 3-year-old or the vehicle’s belt systems. The agency believed that while it might be hypothetically possible that a restraint that passed FMVSS No. 213 when tested with a dummy could fail when restraining a child weighing slightly more than the dummy, on balance, the possibility of such a failure is outweighed by the safety risk of forcing children into restraints that might not adequately restrain them.

NHTSA reaffirms the conclusions reached in that rulemaking and concurs with the views of TraumaLink and AAP that information on tests with current test dummies does not indicate a need to restrict recommending child restraints for children weighing more than the test dummies used to test the restraint. As to CU’s suggestion for developing dummies that reach the maximum weight recommended for a restraint or requiring the addition of ballast weights to existing dummies, this suggestion is beyond the scope of the present rulemaking.

e.  Injury Criteria

1.  Post-NPRM Testing

i.          JPMA

In its comment to the NPRM, JPMA stated that it had conducted a series of 80 sled tests at Veridian Engineering in response to the proposal, to try to understand how the proposed dummies performed compared to the dummies currently in use. The tests also evaluated the proposed changes to the standard bench seat, as well as the proposed injury criteria. JPMA described its test plan as including all test modes for all of the proposed dummies with representative samples of all types of child restraint/harness combinations and installation methods, including lap belt only, lap/shoulder belt, and LATCH. JPMA acknowledged that: "While a total of 80 tests were conducted, this series only begins to explore the results of the proposed changes and does not allow analysis of the net effect of each change, nor does it provide enough history to define the potential variability in test results which could occur. Much more testing is required to define the new effect of each change and the potential variation which can have a significant impact on design and ability to define compliance margins."

ii.         NHTSA Series I and II

PAX conducted a series of dynamic sled tests for NHTSA to evaluate the performance of various child restraints on the revised test seat assembly. The tests used the CRABI and Hybrid III 3-and 6-year-old dummies to evaluate whether these dummies could meet the proposed scaled HIC, chest injury limits and Nij measures. Time and resource considerations limited the testing to 5-point harness rear-facing infant seats, convertible safety seats, and belt-positioning seats. Restraints were evaluated while installed using a lap belt, a lap/shoulder belt, and the LATCH system. HIC measurements were obtained, but testing problems arose with respect to the neck injury and chest deflection data. Because of these problems, NHTSA conducted a second series of dynamic sled tests at VRTC to replicate the tests performed at PAX with the 3- and 6-year-old dummies. These tests were conducted using the same type of child restraints.

iii.        Results of JPMA and NHTSA Series I and II

The charts provided in a docket submission titled "Comparison of PAX/VRTC and JPMA Sled Tests" summarizes the results of the testing performed by both NHTSA and by JPMA. For HIC and chest acceleration, results are presented for both the proposed scaled injury limits and for the same tests using the existing injury criteria limits stated in FMVSS No. 213. Because  chest deflection and Nij limits are not currently specified in FMVSS No. 213, the only charts provided are for the proposed criteria limits.

NHTSA testing performed at PAX and VRTC, described in the NPRM, resulted in dummy responses that were generally within the injury limits proposed in the NPRM, with the exception of Nij. (While acceptable Nij readings were found in tests using the Hybrid III 3-year-old dummy, there were widespread failures in both rear-and forward-facing tests using the CRABI 12-month old dummy and each of four tests with the Hybrid III 6-year-old dummy.)  However, the test results presented by JPMA were quite different. JPMA’s testing, using the revised test seat assembly and new dummies as NHTSA tested, but across a wider variety of child restraint types, showed very mixed results. In many instances, the measured injury parameters either exceeded or marginally passed the scaled injury limits proposed in the NPRM. Further, there were many JPMA tests that resulted in either failing or marginal results when using the existing injury criteria. This raised questions regarding the combined effect of the changes to the test seat assembly, incorporation of the new dummies, and use of the scaled injury criteria limits together.

iv.        NHTSA Series III

In an effort to determine if the use of varying restraint types in the JPMA testing (as opposed to NHTSA’s use of 5-point harness restraints only) could be identified as the predominant factor in explaining the disparity between the JPMA and NHTSA test results, NHTSA conducted a third series of sled tests. These tests were performed at VRTC, and attempted to closely parallel the testing performed by JPMA. In addition to a number of additional 5-point harness restraints, NHTSA also tested forward-facing convertible overhead shield child restraints, and shield-type boosters both with and without the shield.

A total of 20 additional tests were conducted in this third series of sled tests. The results of this series of sled tests more closely paralleled those found in the JPMA tests, in that a wider range of failing and marginal test results were seen as compared to the predominately passing results seen in the PAX test series. The testing of 5-point harness restraints at PAX resulted in injury values that were predominately within the established or proposed limits (with the exception of Nij). However, the VRTC Series III tests showed a wider variation in both marginal and failing responses that appear to be a result of the restraint type that was tested, even though all restraint types meet the current FMVSS No. 213 requirements and appear to be equally effective based upon field studies. Not all VRTC results were similar to those of JPMA, however, as the HIC₁₅ results for the CRABI dummy were typically better in the VRTC tests than in the JPMA tests. Overall, the VRTC follow-on tests did confirm the wider range of test results found in the JPMA testing. The follow-on testing results can be found in the docket.   

2.  Comments and Conclusions

i.          Head Injury Criterion (HIC)

The agency received widely divergent comments on the proposal to limit measurement of HIC to 15 milliseconds and to use the injury criteria of Standard No. 208 that were scaled for children. The Alliance, UMTRI and SafetyBeltSafe supported the use of a 15 ms limit on the head injury criterion (HIC) limit as a more realistic way to assess head and brain injury, with the lower HIC values proposed for each dummy. In contrast, Advocates stated that it was "reluctant to change the duration of HIC measurement from 36 ms to 15 ms without more definitive evidence that this change would not inhibit accurate HIC measurements associated with non-contact head injuries."  Advocates suggested that NHTSA should scale the injury assessment reference values for children even if the agency decides not to shorten the HIC measurement duration, to "take into account the different anatomy of children."  Ford stated that, while the purpose of the 15 ms limit on the HIC calculation interval is to try to differentiate between HICs caused by hard head contacts and non-contact HICs due to head whipping, the 15 ms HIC measurement should not be used to differentiate between non-contact and "chance contact" of the dummy’s head with the dummy’s knees.

JPMA stated that it was willing to consider supporting a 15 ms limit (HIC₁₅), if the agency can undertake research to assure that there will not be unintended consequences from countermeasures needed to meet HIC₁₅. However, JPMA did not support the other proposed new injury criteria, including the scaled HIC values. The commenter stated that the tests of child restraints it conducted with the proposed CRABI and Hybrid III dummies produced injury reference values that exceeded the proposed limits, which the commenter said is a concern given the high level of effectiveness of current child restraints. The commenter suggested that it might be more feasible to use the FMVSS No. 208 criteria in FMVSS No. 213 if the agency were to specify a "more realistic crash pulse for FMVSS No. 213, such as the one contained in the FMVSS No. 208 sled test."  Graco questioned why the scaled HIC values would be applied to in-position child restraint testing if they were derived from out-of-position occupant airbag testing. Graco believed that the values might not be "applicable to child restraint testing with a 213-style pulse."  The commenter stated that it saw minimal benefit to child passenger safety from using the proposed injury criteria. It was concerned that some seats that have historically performed well in the real world and in compliance testing would fail the new criteria.

Response: This final rule retains the existing FMVSS No. 213 HIC threshold of 1000 for the CRABI 12-month-old and Hybrid III 3- and 6-year-old dummies.

Since the TREAD Act directed NHTSA to consider adopting the scaled injury criteria adopted by the May 2000 final rule on advanced air bags, NHTSA proposed that the HIC limits of 390₁₅, 570₁₅ and 700₁₅ be incorporated into FMVSS No. 213 for tests with the CRABI 12-month-, and Hybrid III 3- and 6-year-old dummies, respectively. However, NHTSA believed that it should take a cautious approach in modifying the head injury tolerance level set by the HIC requirement. The agency requested comments on issues related to the proposed injury criteria, such as on what risk levels are acceptable, what factors should be considered in selecting performance limits and whether the same limits as in FMVSS No. 208 should be established for the child restraint standard. The agency noted that the two standards address different sources of potential harm to children. The injury criteria for children in FMVSS No. 208 are intended to minimize the risk from a deploying air bag (ensuring that the air bag deploys in a manner much less likely to cause serious or fatal injury to out-of-position occupants). The injury criteria in FMVSS No. 213 are intended to limit the severity of forces imposed on a child during a crash. Child restraints meeting these criteria have worked effectively to maintain high levels of performance in crashes. Because the injury criteria of the standards are intended to minimize risks from different injury sources, the agency stated that it might be reasonable to have non-identical criteria.

In this final rule, NHTSA has decided against incorporating the scaled injury limits used in FMVSS No. 208 because the data obtained from the JPMA and NHTSA (series III) test programs indicate that current child restraints generally do not meet the proposed limits. There are several reasons why this was a concern for the agency. First and foremost, child restraints are currently highly effective in reducing the likelihood of death and/or serious injury in motor vehicle crashes. The agency was unable to identify a safety problem that the scaled injury limits of FMVSS No. 208 would remedy.

Second, it is unknown what modifications to child restraints would be necessary for the restraints to meet the proposed injury limits. Commenters did not provide information on how child restraints that failed to meet the proposed Nij and other limits could be modified to meet the criteria. Assuming that the restraints could be redesigned to meet the proposed injury limits, there would likely be costs associated with the redesign which would result in increases in the price of the restraints. As noted above in section IV of this preamble, the agency considers the consumer acceptance of cost increases to child restraints (an already highly-effective item of safety equipment) in determining the net safety effects of changes to the child restraint standard. In balancing the effects of meeting the scaled injury criteria against the possible impacts on the price of restraints, the agency determined that the net effect on safety could be negative in this instance because of the minimal benefits of such a change, weighed against the delayed replacement of old restraints by current owners or non-purchase by non-owners. For these reasons, in accordance with the TREAD Act, we have considered whether to apply scaled injury criteria performance levels developed for FMVSS No. 208 to child restraints and have determined it would not be prudent to do so.

NHTSA is adopting HIC₃₆ with a limit of 1000 for all tests with the Hybrid III and CRABI dummies. This final rule does not adopt the 15 ms window that was proposed in the NPRM. This is because the shorter time interval would likely substantially reduce the values calculated for the HIC in compliance tests. Further, as discussed later in this section, NHTSA is not incorporating a neck injury criterion into FMVSS No. 213. A 36 ms time interval to measure HIC allows the HIC measurement in FMVSS No. 213 to capture risk of neck injury indirectly. Given that the agency is declining to adopt a neck injury criterion at this time, the longer measurement window associated with HIC_36, as opposed to HIC_15, will provide reasonable assurances that a child’s neck will not be subjected to excessive forces in a crash. The 36 ms time interval to measure HIC is consistent with the injury threshold used in FMVSS No. 208 for the Hybrid III 50^th percentile dummy prior to the incorporation of scaled injury limits and Nij for advanced air bags.

Limiting the duration over which HIC is calculated to a maximum of 36 ms, while limiting HIC to 1000, assures that the acceleration level of the child’s head will not exceed 60 g’s for any period greater than 36 ms. The 60 g acceleration limit was set as a reasonable head injury threshold by the originators of the "Wayne State Tolerance Curve, which was used in the development of the HIC calculation.

The change to a 36 millisecond time measurement for HIC will not necessarily result in lower HIC values in compliance testing because of the changeover in this rulemaking to the new dummy family. NHTSA compared the differences between using the HIC₃₆  criterion in testing with the Hybrid III dummy family and using the existing criterion, HIC_unlimited, in testing with the Hybrid II family. The following tables outline the results of comparison tests performed on identical child restraints, using the FMVSS No. 213 proposed (Table 8) and existing seat assemblies (Table 9), with both Hybrid III and Hybrid II 3-year-old dummies.

TABLE 8: COMPARISON TESTS OF 3-YEAR-OLD
HYBRID III AND HYBRID II DUMMIES
ON PROPOSED SEAT ASSEMBLY
Hybrid III HIC₃₆ vs Hybrid II HIC_Unlimited
3-Year-Old Child Dummy
(Tested Using with The NPRM Proposed Seat Assembly)

* HIC₃₆ were not calculated, the relationship HIC₃₆  = 0.97 * HIC_Unlimited  was used  to approximate HIC_36.

TABLE 9: COMPARISON TESTS OF 3-YEAR-OLD
HYBRID III AND HYBRID II DUMMIES
ON EXISTING SEAT ASSEMBLY
Hybrid III HIC₃₆ vs Hybrid II HIC_Unlimited
3-Year-Old Child Dummy
(Tested Using Existing FMVSS No. 213 Seat Assembly)

In some of the tests Hybrid III HIC₃₆ results were higher, and in other tests the HII HIC_unlimited results were higher. On the other hand, in a limited number of tests with the 6-year-old dummies, the Hybrid III HIC₃₆ numbers were higher.   All in all, the agency determined that the data are inconclusive as to any differences in how the Hybrid II and Hybrid III dummies measure HIC.  In any event, the agency’s tests of child restraints has not found any difference between HIC_unlimited and HIC₃₆ in terms of compliance passage rates. Thus, the agency has concluded that the impact on child restraint performance relating to the change to HIC₃₆ will be insignificant.  

ii.         Chest Injury Criteria

Some commenters supported while others opposed the proposals to adopt a new chest deflection criterion and to adopt the chest acceleration limits that were scaled for children and incorporated into FMVSS No. 208. The Alliance supported the proposals.   Ms. Bidez supported the proposed chest deflection criteria, stating that "although no significant reports of chest injury in children have yet occurred, prudence and systems engineering dictates [sic] that excessive chest deflection be monitored to prevent the introduction of ‘new’ injury mechanisms in the quest to prevent other injury mechanisms with improved restraint design." 

JPMA opposed the proposed chest injury criteria for the reasons explained in the preceding section. TraumaLink also opposed incorporation of the proposed chest deflection and reduced chest acceleration limits, because according to data it has collected in its study, "These types of injuries do not occur in children in [child restraint systems]."  TraumaLink further stated: "We are concerned about the tradeoff between including these more restrictive thoracic criteria and reducing the overall protection of the head through increased head excursions and accelerations."  These concerns were echoed by UMTRI, which stated that the relationship between the chest deceleration and deflection limits and field injuries under the type of loading simulated in FMVSS No. 213 are not well established. "Introducing these injury criteria now [including neck injury] could lead to counterproductive child restraint designs because many restraints that perform well in the field, particularly booster seats, are likely to exceed the new injury tolerance measures." 

SafetyBeltSafe also opposed the proposed chest injury criteria. It expressed concern that the new seat bench assembly has an added slope to the seat cushion that results in a "harder stop as the restraint bottom[s] out against the plywood platform."  The commenter was concerned that, if the chest acceleration limit were reduced, child restraints that are already close to the current limit could fail the test with no change in how they actually perform in the field. "To counteract this possibility [of failing the test], a manufacturer could soften the system, allowing more head excursion (due again to the geometry change), to keep the chest acceleration in check. This would obviously be counterproductive to child safety."  In addition, SafetyBeltSafe believed that the proposed chest deflection limit "does not relate to any evident injury among restrained child passengers" and thus would not advance child safety. JPMA, UMTRI and SafetyBeltSafe suggested that the agency collect data on chest deflection to establish a database that could be used to evaluate these measures more in the future.

Ford stated that in its sled tests of booster seats using the Hybrid III six-year-old dummy and the FMVSS No. 213 sled pulse, none of the tested boosters could be certified as meeting the proposed limits. "Boosters that showed good shoulder belt fit routinely measured chest acceleration at or near the 60 g limit and chest deflection very near the 40 mm limit. Dummy chest values were sometimes below the compliance limit, but were seldom far enough below the limit to provide a reasonable compliance margin."  The commenter believed that boosters do improve child safety when used properly, and that "if dynamic testing of boosters is continued, the test procedure needs a major overhaul to effectively differentiate between acceptable and unacceptable designs."

Response:  This final rule does not adopt the proposed chest injury criteria relating to acceleration and deflection. A safety need for adopting the proposal has not been established. NHTSA is persuaded by the commenters that there are not sufficient data that demonstrate that children have been seriously injured due to excessive chest acceleration or deflection in current restraint designs. Historically, the majority of child injuries are to the head as opposed to the chest. The agency is concerned about possible negative effects of adopting the proposed chest injury criteria on increased head excursion, as noted by SafetyBeltSafe. Further, not enough is known about the countermeasures that could be employed to meet the proposed criteria. If child restraint manufacturers were to redesign their restraints to meet such requirements, the agency is concerned about the possibility of those revised designs compromising other aspects of the occupant’s injury protection.

The data presented by JPMA, and to a lesser degree, the follow-on tests conducted at VRTC, show difficulty for current restraints to meet the scaled chest criteria, and also show problems for certain restraint types to meet the existing requirements with the revised test seat assembly and new dummies. Redesigning the restraints to meet the requirements, assuming such redesign is practicable, would involve a cost increase to manufacturers, which would be passed on to consumers. The agency does not believe that the cost increase is justified in this instance, and is concerned about the possible effect the cost increase could have on the purchase and use of child restraints. For the aforementioned reasons, we conclude that it is not in the interest of safety to adopt the chest injury criteria developed for FMVSS No. 208 into FMVSS No. 213.

iii.        Neck

Virtually all parties commenting directly on this aspect of the proposal opposed the modified Nij neck criterion (modified from the criterion in FMVSS No. 208 in that the limits on axial force were excluded). The Alliance stated that it believes that serious neck injuries in child restraints are most likely caused by excessive upper neck tension, and not by exceeding the proposed Nij criterion. The commenter thus suggested the agency should specify neck tension and compression limits, as follows, when testing with the CRABI 12-month-, the HIII three-year- and the HIII six-year-old dummies, respectively: 780, 1430 and 1890 N for peak tension; and 960, 1380 and 1820 N for peak compression. The Alliance further stated, however, that applying these limits while maintaining the current sled pulse is likely to make compliance with the requirements impossible or possible only with substantial cost increases. The commenter suggested that NHTSA modify the crash pulse "to make it more representative of the current crash environment" instead of eliminating neck tension. Ms. Bidez stated that "Nij does not appear to predict cervical distraction injuries in children…."  The commenter suggested that "the duration of the axial distraction load as influenced by the presence or absence of adequate torso restraint appears to be a more valid predictor of [spinal cord injury without radiographic abnormality] SCIWORA injuries among children in the absence of head contact."

JPMA, SafetyBeltSafe, UMTRI, TraumaLink and others did not support adopting the proposed Nij criterion at this time. SafetyBeltSafe believed that neither Nij as proposed nor Nij with a limit on tension should be used as a compliance criterion unless these are proven to be useful predictors of child neck injury. UMTRI believed that Nij should not be incorporated at this time because the relationship between the criterion and real-world injuries "under the type of loading simulated by FMVSS 213 are [sic] not well established."  The Insurance Institute for Highway Safety (IIHS) was concerned that studies of real-world crashes indicate that neck injuries due to inertial forces appear to be rare, yet, the commenter stated, it is not clear how child restraints could be better designed to lower neck injury measures. Ford stated that, in its sled tests of booster seats, "Upper neck tensions and extension moments above the FMVSS 208 criteria were also routinely measured. Every test exceeded at least one of the Nij limits." 

TraumaLink was concerned about the state of knowledge about pediatric neck injury and suggested that not enough was known to proceed at this time. The commenter stated that data on the biomechanical response of the pediatric neck to trauma are severely limited and as a result, the neck of current child dummies may not be representative of the real child. The commenter also believed that efforts to include pediatric neck tolerance levels in regulatory efforts are scientifically premature. TraumaLink further stated:

More research is needed to understand the movement of the child’s neck in traumatic events and the likelihood for injury before enacting regulatory standards, but our results indicate that this work is of paramount importance. We believe that this research may reveal the importance of neck tension and suggest that exclusion of limits on peak tension in the test procedure is not appropriate. Therefore, we feel that the neck injury measures should be calculated but not used in the pass/fail criteria in the FMVSS 213 test to build the fund of knowledge needed to further refine the injury measure.

Similarly, commenters JPMA, SafetyBeltSafe, UMTRI and the IIHS suggested that more research is needed on neck injury among restrained children. Some of these suggested that NHTSA measure neck force and moment parameters during compliance tests to become familiar with the range of results.

Response: The agency has decided not to incorporate Nij into FMVSS No. 213 compliance tests at this time. Both NHTSA and JPMA testing has clearly demonstrated that existing child restraints that have historically performed very well in the field can not meet the proposed neck injury limits in the majority of test cases. Neither NHTSA nor child restraint manufacturers have identified any countermeasures that could be incorporated into existing designs that would promote compliance with the proposed requirements. Further, NHTSA agrees that there is a lack of injury data to demonstrate a need to incorporate neck injury criteria at this time. As discussed in the section regarding head injury criterion, the adoption of a 36 ms measurement window for HIC, as opposed to the 15 ms window that was presented in the NPRM, will also serve as surrogate of sorts for a neck injury criterion to ensure that children continue to be well protected.

NHTSA does not believe that enough is known regarding neck injury for children at this time. As the agency is not proposing the incorporation of Nij in this final rule, NHTSA likewise does not feel that it is appropriate at this time to specify neck tension limits or any other neck criterion. These are areas where the agency could perform additional research in the coming years, as warranted by a safety need and the demands on the agency’s resources.

In accordance with the TREAD Act, NHTSA has considered adopting the neck injury criteria developed for FMVSS No. 208 into FMVSS No. 213. For the aforementioned reasons, we conclude that incorporating the criteria into Standard No. 213 is not warranted at this time.

f.  Leadtime

The TREAD Act required NHTSA to complete this rulemaking by November 1, 2002. With that date in mind, the agency made the following conclusions about the dates on which compliance with the requirements will become mandatory.

a.  NHTSA believes that manufacturers could begin certifying their child restraints based on testing done on the new seat assembly and pulse in approximately 2 years (i.e., the effective date for the change will be August 1, 2005). NPRM proposed a 2-year leadtime, which Graco supported. While the agency does not expect the changes to the seat assembly to have a major effect on the results of compliance tests, restraint manufacturers will likely have to conduct testing to confirm compliance of their restraints. This will be a financial impact on the manufacturers that could be spread out over a 2-year time period. The agency does not anticipate any lives saved or injuries avoided from the amendment.

b.  This final rule provides for about a 2-year effective date for the requirement to use the new CRABI and Hybrid III dummies in compliance tests (the effective date for the change will be August 1, 2005). The agency does not expect that the changes to the dummies will have a significant effect on the results of compliance tests, with the exception of some infant-only car seat/carriers. However, restraint manufacturers will likely have to conduct testing to confirm compliance of their restraints. This will be a financial impact on the manufacturers that could be spread out over a 2-year time period. Some infant-only restraints do not have backs high enough to support the CRABI 12-month-old dummy and will thus have to be redesigned.

The agency cannot estimate any lives saved or injuries avoided from the amendment. 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 having infant car seat/carriers be designed with higher back support structures.

c.  As for using the weighted 6-year-old dummy to test restraints (typically booster seats) recommended for children with masses of over 22.7 kg (weights over 50 lb), this rule specifies a 2-year leadtime for the requirement (the effective date for the change will be August 1, 2005). We do not anticipate that manufacturers will have to redesign their booster seats or safety harnesses to certify compliance using the dummy. However, the rulemaking to incorporate the weighted 6-year-old dummy into Part 572 is not complete, so the effective date is provided to account for the completion of that rulemaking. (The Part 572 NPRM was published May 7, 2003; 68 FR 24417.)

d.  Manufacturers are permitted the option of voluntarily using the new sled assembly and pulse and the new test dummies prior to the date (August 1, 2005) on which they would be required to do so. Note, however, that this final rule also specifies that a manufacturer’s selection of a compliance option (e.g., to use the new dummies prior to the mandatory compliance date) must be made prior to, or at the time of the compliance test and that the selection is irrevocable for that child restraint. This provision is needed for NHTSA to efficiently carry out its enforcement responsibilities. The agency wants to avoid the situation of a manufacturer confronted with an apparent noncompliance (based on a compliance test) with the option it has selected responding to that noncompliance by maintaining that its products comply with a different option for which the agency has not conducted a compliance test. To ensure that the agency will not be asked to conduct multiple compliance tests, first for one compliance option, then for another, this rule requires manufacturers to select the option by the time it certifies the child restraint system and prohibits them from thereafter selecting a different option for the restraint.