As is often shown in our book, the LATCH Manual (and, perhaps, even demonstrated by the fact that it is now in its seventh edition), the potential of LATCH has been limited over its first 10 years by many unfortunate usage complexities, despite the fact that it has brought some improvements to child safety.
Chief among these complexities is the fact that there are multiple sources of advice on the anchor weight limit when installing a CR using LATCH in any given child/CR/vehicle scenario. Attempts to follow both manufacturers’ advice on this subject are often thwarted by guidance that is contradictory, vague, and/or nonexistent.
If it is a fact that anchor failure is a genuine risk at some child weights within the range of today’s CRs, as has been communicated to the CPS community, then instances where there is a lack of clear guidance on weight limits could lead to potentially dangerous misuse. If, as others contend, LATCH could safely be used to higher weights than some of the limits that are currently stated, then this must be confirmed and communicated by the manufacturers before LATCH can be used at these weights.
Whichever is the case, the current situation of mixed messages should not be tolerated for yet another ten years. The public must have one, clearly-communicated source for LATCH weight limits, and that source must be definitively established through improvements to FMVSS 213 and 225 requirements. SRN feels that this problem must be resolved so that LATCH use can reach its full, life-saving potential. We are particularly concerned about usability of top tethers, which play a critical role in reducing injurious head contact in a crash.
One fact that creates confusion, and which should be addressed by NHTSA, is that current FMVSS 225 strength requirements for LATCH anchor hardware cannot be clearly equated to a child occupant’s weight. To meet the standard, the vehicle manufacturer must test anchors to ascertain that they meet a minimum load threshold, and, though this load can be mathematically converted to a weight, that number indicates not only the child occupant weight, but also the weight of the CR. CR design elements can also influence anchor loads. To further complicate attempts to pinpoint a child weight based on FMVSS 225 requirements, the specified test procedure for anchor strength is quasi-static (over multiple seconds), rather than dynamic (as a CR test or real crash would be), which makes a difference when applied to the type of metal used for making anchor hardware. Also, the requirements are different for lower anchors versus tether anchors, creating potential variations even among the three anchor points within one LATCH system.
Another issue is that FMVSS 213 is outdated in that it does not require adequate testing of the high-weight-harness CRs available today. The current standard applies only to CRs for children up to 65 pounds. Also unfortunate is the fact that the FMVSS 213 test requirements for CRs for use from 50 to 65 pounds exclude performance measures, largely due to the limitations of the available dummies. (See Safe Ride News March/April 2011 for a related article on dummies.) Assurances from CR manufacturers that voluntary testing at higher harness weights is taking place are comforting, but the fact remains that no actual rule is in effect to require testing of important injury measures like head and knee excursion for CRs rated for use over 50 pounds.
The LATCH Working Group, at the time of its formation in 2006, held promise for reaching solutions to at least some of these problems related to LATCH limits via a cooperative, nonregulatory approach. However, though this voluntary consortium of both vehicle and CR industry representatives did contribute to improvements on other LATCH issues, the progress of this group was stalled by the economic crisis in late 2008. The group’s planned research on this important subject, aimed at better assessing anchor load limits, now holds little promise for resolution of these issues in any timely manner.
So, it is time for NHTSA to take action through rulemaking. We need amendments to our regulations that will reflect the CRs in use today, identify the source of LATCH anchor weight limit information, and specify how that information will be clearly communicated to the public.
—Denise Donaldson ©Safe Ride News March/April 2011