2024-31142. Federal Motor Vehicle Safety Standards; Child Restraint Systems, Child Restraint Anchorage Systems, Incorporation by Reference

Table 1—Summary of Tether Anchorage Location With Respect to the NPRM's Proposed Allowable Tether Anchorage Zone and That Determined as a Plane 120 mm Behind the H-Point

Year	Manufacturer	Model	Seat position	Current zone	NPRM zone	Final rule zone (120 mm behind H-point)
2015	Toyota	Sienna	2nd Row Driver Outboard	Pass	Fail	Pass.
2018	Freightliner	Sprinter	2nd Row Passenger Outboard	Pass	Fail	Pass.
2020	Ford	Transit	2nd Row Passenger Outboard	Pass	Fail	Pass.

The NPRM's proposed requirement sought to eliminate tether anchorages located deep under the seat where folding the seat is necessary to reach it. NHTSA believes the limit on the tether anchorage location under the seat defined by a vertical plane 120 mm rear of the H-Point meets this intent. NHTSA also concludes that using a vertical plane 120 mm rearward of the H-point is easily defined, removes ambiguities commenters noted in the NPRM's proposed tether anchorage zone, and better reflects the accessibility and usability of the tether anchorages. Therefore, the agency is adopting requirements to specify the allowable tether anchorage zone under the seat using a vertical plane 120 mm rear of the H-Point to define the allowable limit. This requirement will prevent tether anchorages from being located deep under the seat where they are difficult to access, addressing comments received.

b. Tightening the Tether

NHTSA proposed requirements to make it easier for a consumer to attach a child restraint tether hook to a tether anchorage and tighten the tether strap. Currently, FMVSS No. 225 specifies that tether anchorages must be located within the shaded zone shown in figures 3 to 7 of the standard for the DSP ( print page 1306) in which the anchorage is installed.^[86] NHTSA proposed to amend FMVSS No. 225 to require that tether anchorages have clearance space for tightening the strap.

The NPRM proposed to require a 165 mm (6.5 in) minimum distance from each tether anchorage to a seat-based reference point for each designated seating position (DSP) with a tether anchorage. In 2012 the LATCH Usability study ^[87] found that, under the current FMVSS No. 225, tether anchorages can be located too close to the head restraint, on top of the seatback, or the tether attachment point on a CRS, resulting in insufficient clearance to tighten the CRS tether strap. The study reviewed the tether hardware assembly on 21 child restraint systems made by 11 different CRS manufacturers.^[88] The review found the tether hardware assembly of the 21 child restraints ranged from 102 to 184 mm (4 to 7.2 in) in length, with 15 CRSs having tether hardware assembly lengths between 140 mm (5.5 in) and 165 mm (6.5 in). The study suggested that having tether anchorages on a package shelf or behind the seatback at a distance of at least 165 mm (6.5 in) rearward or below the back of the head restraint or top of the seatback for DSPs without a head restraint would provide greater clearance for attaching the tether hook of a CRS and tightening the strap.

In drafting the NPRM NHTSA reviewed the LATCH usability study and tentatively determined that specifying a minimum 165 mm (6.5 in) distance from the tether anchorage to a defined reference point on the vehicle seat would improve tether anchorages' ease-of-use. The NPRM explained that this clearance would allow for the tightening of tether straps in most vehicles without interference from other structures, such as the head restraint.

The NPRM proposed that the reference point on the vehicle seat, which NHTSA designated as “SB,” be defined as the intersection of the plane parallel to the torso line reference plane (defined in figure 3 of FMVSS No. 225) that passes through the rearmost point of the seat and the wrap-around line from the “V-point” to the tether anchorage.^[89] The agency noted that both the V- and W-point could have been used for determining the vehicle seat reference point SB. NHTSA selected the V-point to define the reference point because it would encompass both low mounted and high-mounted tether straps.

1. Tether Anchorage Location—165 mm to a Reference Point

Comments on 165 mm Distance to Reference Point

In response to the NPRM many vehicle manufacturers stated that requiring manufactures to move tether anchorages to locations meeting the 165 mm (6.5 in) specification is impractical within current styling because substantial vehicle components currently occupy the locations. The Alliance stated that the relocation of a single component has implications for other design considerations including, but not limited to, wiring harnesses, body in white attachments and reinforcements, electromagnetic interference, and radio-frequency interference re-qualification. FCA stated that moving the tether anchorages rearward would force a complete redesign of the package shelf, including re-packaging of the existing package shelf components as well as moving the reinforcements. FCA said that if speakers or modules must be relocated to the door or the trunk changes to these components would also be necessary, including side impact countermeasures, door electrical wire harnesses, and interior trim modifications. The Alliance added that many passenger cars with tether anchorages located in the package shelf behind the seat will not meet the proposed 165 mm minimum wrap around distance,^[90] even though the anchorages are easy to use.

Many vehicle manufacturers, the Alliance, and Global stated that tether anchorage distance and CRS hardware incompatibility should be addressed in FMVSS No. 213 by limiting the size of the tether hook and other CRS attachment hardware.^[91] Some vehicle manufacturers and the Alliance provided data on the sizes of tether hooks and hardware in stating that the lack of uniformity in CRS attachment hardware and its mounting location on the CRS point to the actual source of the compatibility issue, rather than the vehicle “swing zone” behind the seatback or head restraint. Hyundai stated that tight installations can be achieved even with vehicles that have less than the proposed 165 mm (6.5 inches) distance, with a CRS tether hardware and strap measuring 170 mm (6.7 inches).

The Alliance and Toyota identified potential problems with applying the proposed procedure to certain vehicles regarding the definition of the point SB. They presented a case for some head restraints where the torso reference plane may not intersect the strap wrap around line. Therefore, for this type of head restraint, the reference point SB does not exist. The Alliance and Toyota also presented a case in which the reference point SB cannot be defined when the seatback angle is larger than the torso angle.

Toyota requested that NHTSA develop a repeatable and feasible requirement regarding the distance from the tether anchorage to the DSP. Toyota suggested that because the existence of reference point SB is dependent on the rearmost point of the seat, which can vary dramatically based on seat design, one potential method to solve this issue would be to develop a new tool to measure the distance of 165 mm from the tether anchorage instead of using the concept of reference point SB.

Several commenters also suggested an alternative way of defining a clearance zone. FCA recommended a general redefinition of the reference point SB without providing a suggested definition. The Alliance opined that the proposed minimum wraparound distance, measured from point SB, is unnecessarily stringent and does not take current CRS installation practices into account. The Alliance and Honda recommended that a point farther forward in the vehicle DSP, representing a tether attachment point on a child restraint, would provide a more practicable reference point for this measurement.

Britax stated that mandating a minimal vehicle interior distance should facilitate better tether ( print page 1307) installation, particularly in sedan vehicles with rear windows close to rear seatbacks. Britax anecdotally noted it has experienced situations where the distance between the vehicle seat and tether anchorage would not permit proper tether attachment and tightening. UMTRI supported the implementation of a 165-mm clearance around the tether anchorage in vehicles and the regulation of a maximum adjusted length of the tether attachment hardware to 165 mm to improve compatibility. UMTRI noted that these recommendations were based on usability testing of CRS with a single strap tether.

Post NPRM Research

UMTRI Research

After carefully reviewing comments that raised concerns over the proposed 165 mm tether anchorage clearance criterion, the agency determined that it was appropriate to task UMTRI with conducting a study ^[92] to: (1) define an alternate reference point to the proposed SB point that would be more practical, (2) ensure that the requirements do not interfere with Australian Design Rule (ADR) 34/2,^[93] (3) estimate the number of vehicles that may need modification to meet clearance criteria based on the proposed and alternative reference points, and (4) evaluate alternative ways of ensuring tether tightness.

In carrying out its study UMTRI used two data sets to estimate the proportion of vehicles that would meet the proposed 165-mm clearance criteria. First, UMTRI surveyed 60 top selling 2012-2013 MY vehicles to collect data on each vehicle's tether anchorage location, head restraint characteristics, and tether routing path. UMTRI used a rigid 165-mm gauge with tether hook to evaluate whether the tether anchorage location met the proposed criteria. This data set showed that 21 of the surveyed vehicles had tether anchorages on the rear package shelf. Eighteen of these vehicles were sedans and three were pickup trucks. Of the sedans, only one met the proposed criteria. For the 17 sedans that did not meet the NPRM's proposed criteria, routing the tether over the head restraint improved access to the tether hardware.

UMTRI surveyed photos of the 21 vehicles with a tether in a package shelf to evaluate potential barriers in moving the tether anchorages. About half of the vehicles had no visible barriers at outboard seating positions, two vehicles had potential for interference from rear window glazing during installation, and the remaining vehicles had speakers in the way. The center seating position in 5 vehicles had rear defroster structures that may be in the way of relocation.

The second data set used a survey of 98 top selling 2010-2011 MY vehicles. The tether anchorage location was measured for these vehicles via wraparound distance relative to an estimated shoulder reference point. These surveys collected photos that helped identify structures that would hinder any tether anchorage relocation if the 165 mm criterion was not met. Data from the 98 vehicle-dataset showed that 44 percent of vehicles with the tether anchorage on the seatback would meet the 165 mm criterion. Of the 35 vehicles with the tether anchorages located in the package shelf of the outboard seating position, 24 percent would not meet the 165 mm criterion, but could improve usability if the tether was routed over the head restraint.

UMTRI then developed an alternate reference zone using established reference points such as the H-point (hip point) and the R-point (shoulder point) using 21 vehicles (MY2010-2014) scanned by UMTRI during previous projects.^[94] A circle with a 325 millimeter radius centered on the R-point and truncated 230 mm below its center was used to create the limits of the allowed tether anchorage zone.

UMTRI evaluated 11 SUVs and trucks in the scanned vehicle dataset ^[95] that had an upper seatback tether anchorage location. To avoid conflicts with the IIHS usability rating criteria ^[96] the circle was truncated at 230 mm below the R-point. Doing so allowed for the tether anchorage to be located far enough to ensure tightness while not conflicting with IIHS usability rating criteria.

UMTRI evaluated the proposed and alternative tether anchorage clearance criteria against 20 of the 21 ^[97] scanned vehicles (MY2010-2014) to determine whether vehicles met the proposed distance criteria and quantify the distance a tether anchorage would have to be relocated if that vehicle did not meet the proposed or alternative criteria. Results were mixed.^[98] Eleven models met both criteria. Four failed both criteria but using the alternative criterion the tether anchorage relocation distance was shorter than for the 165 mm clearance criterion. Two passed the alternative criterion but failed the 165 mm criterion. Two vehicles with tether anchorages in the upper seatback (and not the package shelf) passed the 165 mm criterion but failed the alternative criterion. For these two vehicles, tightening the tether was difficult for installing some child restraints. The tether anchorages for these two vehicles would need to be moved 1-2 mm lower to meet the 325 mm truncated sphere zone, which would also permit tightening the tether.

UMTRI also performed in-vehicle evaluations for both tether anchorage clearance criteria on 10 vehicles (MY 2004-2014).^[99] For this set of vehicles UMTRI found that three vehicles failed both criteria, while seven met both criteria. Of the three vehicles that failed both criteria, the distance to move the tether anchorages to meet the alternative criterion was shorter than that for meeting the proposed criterion in two vehicles.

In its review of the two vehicle surveys UMTRI found that about one-third of vehicles had tether anchorages located on the package shelf and that the majority did not meet the 165-mm criteria if the tether strap was specified for routing under the head restraint. However, UMTRI found that in most of these vehicles routing the tether strap over the head restraint provided good access to the tether adjuster hardware.

VRTC Research

Following review of the UMTRI study, VRTC evaluated the alternative criterion (zone based on a 325 mm circle centered on the R-point), the proposed 165 mm clearance distance, and the ( print page 1308) lengths of CRS tether hardware.^[100] VRTC measured six vehicles with various tether anchorage locations in the rear driver side position and rear center position.

Tether Anchorage Measurements

The VRTC Tether Anchorage Measurement results were similar to those found by UMTRI ( see Table 2). The six vehicles' seating positions with package shelf tether anchorages failed the proposed 165 mm distance. Only two of those six tether anchorages failed the alternative criterion. Of the two vehicles that failed both criteria, the needed relocation distance of the tether anchorage to meet the criteria was smaller for the alternative criterion than the proposed criterion. All seating positions with the tether anchorage on the seatback or roof passed both criteria.

Table 2—VRTC Tether Anchorage Vehicle Survey Results

Vehicle			Tether location		325 mm zone (mm)	165 mm tether distance (mm)
Year	Make	Model	Rear driver position (RDP)	Rear center position (RCP)
2010 Ford Taurus			Package Shelf		384	149
				Package Shelf	436	141
2011 Cadillac CTS			Package Shelf		294	68
				Package Shelf	409	74
2016 Toyota Sienna			Seatback		742	757
				N/A	N/A	N/A
2011 Hyundai Sonata			Package Shelf		308	75
				Package Shelf	365	65
2016 Chevrolet Tahoe			Seatback		625	657
				Seat Back	628	637
2016 Nissan Rogue			Seatback		433	469
				Roof	630	460