LATCH Child Seat Connection Safety Questioned
A study published in Traffic Injury Prevention concluded that Lower Anchors and Tethers for Children (LATCH) connections do not offer equal protection to using the vehicles lap/shoulder belt combination to connect rear-facing child safety seats in rear impact crashes.
The study's authors at Robson Forensic, Inc. tested three popular rear-facing infant child safety seats—the Graco SnugRide, the Britax Chaperone and the Evenflo Tribute in rear impact sled tests using three different installations – LATCH, and seat belts with Emergency Locking Retractors (ELR) and Automatic Locking Retractors (ALR). The safety seats were installed in the outboard seating positions of a sled buck representing the backseat of a 2012 Toyota Camry and occupied by a six month old crash test dummy. The researchers were interested in how well LATCH secured the infant seat in comparison to seatbelt installations in a 30 mph rear impact.
High-speed videos in these rear-facing infant seat tests revealed very different kinematics from forward-facing child and adult restraints, namely the rotation of the seat and the dummy around its attachment axis, allowing the "child's head to extend beyond the confines of the car seat in many instances, allowing the head to strike the seatback in which the RFCRS was installed."
These effects were more pronounced in the LATCH configuration, resulting in an increase in angular momentum and rotation and more severe head strikes. The tests looked at Head Injury Criterion (HIC) values, even though there are no Federal Motor Vehicle Safety HIC standards for a six month old infant. But, what is notable in this study is that the HIC values, which are based on acceleration, are much higher in Britax and Graco seats secured with LATCH (60 percent higher in the SnugRide and double in the Britax.) The authors concluded: "the results of this study suggest that LATCH does not offer equal protection to lap/shoulder belts from head injuries in rear impacts when used with infant seat type rear facing child restraint systems."
This study suggests that if caregivers want to use the LATCH system with rear-facing infant seats, they should consider doing so with a tether. Tethers serve a critical purpose in reducing head excursion in a crash and few parents recognize its importance or that it can and should be used in conjunction with lower anchors or seat belts. The study's authors refer to this type of installation in other countries, but apparently did not use tethers in their tests: Swedish rear facing child restraint designs differ from US products, in that they route a tether down and forward to a point on the floor in front of the vehicle seat where the child seat sits. This tethering system limits rotation towards the rear of the vehicle on rebound in frontal impacts or initial impact in rear impacts. By doing this, the forward rotation of the child seat is limited and allowed the child to "ride down" the collision with the vehicle. For many years, rear-facing infant seats in the U.S. did not have tethers. Today, a few brands, including Britax and Combi, include tethers in their rear-facing infant seat design.