The Use of Tethers for Children
Weighing Over 40 Pounds

     Some children over 40 pounds need restraints other than belt-positioning boosters. Child restraints (CRs) with harnesses for children over 40 pounds offer protection in situations where:

• the child needs extra support, positioning, or restraint due to physical or behavioral need (called “special needs restraints”)
  
• •the child has outgrown a conventional CR (at 40 pounds) but is not developmentally ready to use a belt-positioning booster
  
• only lap belts are available (lap belts being considered vastly inferior for occupant protection than systems with upper-body restraint)
  
• parents prefer the enhanced protection of a five-point harness rather than that of a belt-positioning booster (BPB) with a three-point lap-shoulder belt

     Furthermore, there is evidence that children over 40 pounds are continuing to use the harness mode of combination seats (CR/boosters) above 40 pounds. These are made to be used with harness and tether only up to 40 pounds and as a BPB above that weight. There may be several reasons for this misuse, but it seems clear that those parents want to continue harness use rather than switch to the booster mode.
      CRs are now being marketed at retail with the capacity for use by a child weighing 50, 65, or even 80 pounds. CR instructions for these high-weight harness (HWH) child restraints, all of which come with tethers, do not mention anything about the vehicle’s tether anchor capacity. Many vehicle makers, however, limit use of their tether anchors to children weighing 40 pounds or less. This discrepancy puts parents in an awkward dilemma when using HWH-CRs for their children over 40 pounds. If they conscientiously read both vehicle and CR instructions, as is always recommended, they will be faced with deciding whether or not to use the tether.
      When vehicle and CR instructions differ, parents and other caregivers in this situation must be given adequate information to make the decision as to whether to use the tether or not. Removing the tether of a HWH-CR when the occupant reaches 40 (or even 48 pounds) without serious consideration of the issue is not a logical (or appropriate) option.

Tethers for special needs restraints

    For some special needs restraints, the CR manufacturer provides and requires installation of heavy-duty tether anchor hardware. This must be used if at all possible, especially as these CRs usually are intended for a child weighing up to 100 pounds or more. Moreover, the devices themselved are generally quite heavy. Installation of heavy-duty tether anchors recommended by the manufacturer is often complicated and may be beyond the resources of the family or impossible due to incompatibilities with the structure of the vehicle. Vehicle dealerships generally will not install in their vehicles heavy-duty tether anchors made by other companies. Families may get help with installation from members of the National Mobility Equipment Dealers Association (NMEDA, see Resources Section page 240).
     For families unable to use such resources, there may be no alternate tether anchor (other than a safety belt from the row behind, as described earlier in this chapter) instead of a factory-installed or retrofitted anchor. Use of the safety belt in a three-row van or SUV is feasible. Using that method in the front seat of a vehicle with a frontal air bag that has no on/off switch would raise other serious concerns. The CR manufacturer should be consulted.

NHTSA does not specify a maximum weight

     NHTSA, which developed and currently enforces the standards (FMVSS 213 and 225) that cover children in restraints up to 50 pounds and tether (and lower) anchors in vehicles, has not offered guidance concerning a maximum weight limit for standard LATCH anchors despite language in the Federal Register as follows:

“As discussed in previous sections, the agency has based the determination of the maximum strength requirements on assumptions regarding the mass of the system and vehicle decelerations.  Specifically, with respect to the mass of the child, the agency has used 65 lb, as proposed in the TREAD NPRM, which exceeds the current limit of Standard No. 213’s applicability by 15 lb. (emphasis added).” Federal Register, June 27, 2003 [68 FR 38208].

     Despite that statement, the agency has left it up to vehicle manufacturers to state anchor maximums, but has not required them to do so. Many vehicle manufacturers have been very conservative in their published maximum weight limits (40 pounds) as listed in Appendix B and some publish no maximum. As of January 2005, Audi,* DaimlerChrysler, Ford, Porsche, Subaru, and Volkswagen,* state higher (and differing) maximums. General Motors states a 40-pound maximum for the tether when used with a safety belt, while allowing a 48-pound maximum for the LATCH system (lower and tether anchors).
      For lower LATCH anchors, an alternative, the safety belt, exists for installing HWH-CRs. For a tether, however, there is no alternative. In the opinion of a number of safety experts, tether anchors should be capable of restraining weights higher than 40 pounds, based on a careful reading of FMVSS 225 (with its minimum performance standards), dynamic tests, and real-world experience. In addition, a third point of attachment is always better than two.
    The only recourse for a CPST or advocate is to inform the parents of both sides of the issue and allow them to make their own decision regarding use of a tether anchor. Counseling a family to allow a heavier child to ride in an untethered CR would be a poor solution.

* with certain exceptions

Background

     To be prepared for such a discussion with a family, educators such as CPSTs and CPS Instructors (and even customer service personnel) must understand the crash dynamics related to tethers. A tether should be seen as an important part of the primary restraint system for a forward-facing CR, along with the safety belt or lower LATCH anchors. The tether provides an auxiliary anchor, in that CRs for children up to 50 pounds must pass the “misuse” test without a tether attached. However, tethers do reduce head movement in a frontal crash, and this third point of restraint is considered to be increasingly beneficial for children at higher weights and heights. However, seats made expressly for the special health care needs of children do not have to pass such a test, so tether use at any weight is mandatory for most of them.
     The likelihood of a tether failing completely when anchoring a HWH-CR occupied by a child weighing more than 40 pounds is considered highly unlikely and has not been seen in real-world crashes. (Through its crash testing program, Ford has determined that its tether anchors can be used with a conventional CR up to 60 pounds and with a harness/vest up to 80 pounds.) If the anchor, tether hook, strap, or connection to the CR were to fail, it would do so late in the crash sequence. It already would have restricted forward motion of the top of the CR significantly while still attached, absorbing crash energy in the process of deforming, stretching, and/or breaking. Both would result in considerably reduced head excursion compared to what would happen if the CR were not tethered. It should be noted that in the few documented cases of tether failure in extreme dynamic tests, it has often been the hook or the connection point to the child restraint that has failed, not the anchor itself.
     Furthermore, the very slim risk of a tether pulling out in a extremely severe crash should be seen in relation to the substantial benefit of reduced head excursion due to tether use, even in much more common, lower force crashes.
Some manufacturers worry about the rare event in which tether hook or anchor hardware might pull out completely and fly forward, still attached to the tether strap, possibly hitting the child or another passenger. Although this is a theoretical possibility, the very low probability of this happening, combined with the relatively minor injury potential from such hardware (when compared to other injury-producing effects of such a severe crash), is no justification for not using a tether whenever possible. As with some other “warnings” issued by manufacturers, this may be intended to cover all possible injury scenarios that might confront them in court rather than to provide realistic advice.

Conclusion

     The bottom line is that the more anchorage points for a child restraint, the better. While all concerned are looking forward to the availability of more hard data on the performance of tethers on HWH-CRs with higher-weight dummies/children in vehicle crash tests, sled tests, and the real world, the issue of tether use and maximum weights cannot be ignored today. Products have often led the way with innovations that later become part of best practice and then regulatory requirements; one can hope this is one of those situations.
     Parents who seek to use HWH-CRs for children above 40 pounds who do not have special situations mentioned above also should also be informed that belt-positioning boosters (BPBs) offer very good protection and do not require a tether (with one exception). Children who are large enough, developmentally ready, and without physical disabilities requiring upper torso support or other special positioning assistance can use BPBs with confidence. BPBs are easy to use if lap-shoulder belts are available. They have been shown to provide very good protection in real-world crashes.
See Chapter 1, page 8 for a summary of advice for parents and other caregivers on this issue.

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