Effects of LATCH versus Available Seatbelt Installation of Rear Facing Child Restraint Systems on Head Injury Criteria for 6 Month Old Infants in Rear End Collisions

Objective: The Lower Anchor and Tethers for CHildren (LATCH) system was introduced in vehicles made after September 1, 2002 and intended to make installation of rear and forward-facing child safety seats easier. Due to the lack of rear impact testing of RFCRS required per the Federal Motor Vehicle Safety Standards (FMVSS), the purpose of this study was to explore the effects, if any, of installation method of RFCRS on the performance of commonly purchased makes and models of RFCRS. Specifically, we hypothesize that in a 48 km/h (29.8 MPH) rear-end collision, installation of RFCRS using the LATCH system will result in higher Head Injury Criteria (HIC) values when compared to using the available lap/shoulder seatbelt (Emergency Locking Retractor - ELR or Automatic Locking Retractor - ALR).
Methods: The test matrix included 36 rear impact sled tests conducted using 3 installation methods on 3 models of RFCRS: the Graco SnugRide® with and without the base, the Britax Chaperone with base-mounted anti-rebound bar, and the Evenflo Tribute®, a model of convertible rearward/forward facing restraint system used in the rearward facing mode. The seats were installed using the LATCH system, ELR lap/shoulder belts, or ALR lap/shoulder belts in seating positions 4 and 6 on a vehicle buck mounted to the sled test base. The infant seat and 6 month old CRABI anthropometric test device (ATD) installation methods were in accordance with standards set forth in the National Highway Traffic Safety Administration's (NHTSA) FMVSS No. 213, Child Restraint Systems. All tests were conducted on pneumatic controlled acceleration sled (HYGE, Inc., PA, USA) at 48 km/h.
Results: Installation of infant seat type RFCRS using the LATCH system resulted in higher HIC15 values when compared to using the available lap/shoulder seatbelt (ELR or ALR). The mean HIC15 values were most severe when infant seat type RFCRS were installed using LATCH (Graco SnugRide® HIC15 = 394 and Britax Chaperone HIC15 = 133) compared to using either ELR lap/shoulder belts (Graco SnugRide® HIC15 = 218 and Britax Chaperone HIC15 = 65) or ALR lap/shoulder belts (Graco SnugRide® HIC15 = 194 and Britax Chaperone HIC15 = 78). The installation method did not result in a statistically significant difference in HIC for the convertible type RFCRS (Evenflo Tribute®). In many of the tests, the ATD's head struck the seatback in which the RFCRS was installed. These head strikes resulted in the higher HIC15 scores recorded throughout the testing.
Conclusions: 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 RFCRS.

研究目标：儿童下锚绳系统（Lower Anchor and Tethers for CHildren，LATCH）于2002年9月1日后的量产车辆中首次搭载，旨在简化后向与前向式儿童安全座椅的安装流程。鉴于联邦机动车安全标准（Federal Motor Vehicle Safety Standards，FMVSS）未要求对后向儿童约束系统（Rearward-Facing Child Restraint Systems，RFCRS）开展后方碰撞测试，本研究旨在探究RFCRS的安装方式对市售主流型号RFCRS性能的影响（若存在该影响）。具体而言，本研究提出如下假设：在48 km/h（29.8英里/小时）的追尾碰撞工况下，相较于采用现有腰肩式安全带（紧急锁止式卷收器（Emergency Locking Retractor，ELR）或自动锁止式卷收器（Automatic Locking Retractor，ALR））安装的RFCRS，采用LATCH系统安装的RFCRS的头部伤害指数（Head Injury Criteria，HIC）值更高。

研究方法：本试验矩阵共包含36次后方碰撞台车试验，针对3款RFCRS分别采用3种安装方式开展测试：分别搭载底座与未搭载底座的葛莱SnugRide®儿童安全座椅、搭载底座式防回弹杆的宝得适Chaperone儿童安全座椅，以及以反向安装模式使用的可双向（后向/前向）安装的英孚乐Tribute®儿童安全约束系统。受试座椅分别通过LATCH系统、ELR腰肩式安全带及ALR腰肩式安全带，安装于搭载于台车试验台架的车辆假座椅的第4、第6号位。婴儿型安全座椅及6月龄CRABI人体测量试验装置（Anthropometric Test Device，ATD）的安装方式均符合美国国家公路交通安全管理局（National Highway Traffic Safety Administration，NHTSA）发布的FMVSS No.213《儿童约束系统》相关标准要求。所有试验均在美国宾夕法尼亚州HYGE公司生产的气动控制加速台车上完成，碰撞工况速度设定为48 km/h。

试验结果：相较于采用腰肩式安全带（ELR或ALR）安装的婴儿型RFCRS，采用LATCH系统安装的婴儿型RFCRS的HIC15值更高。婴儿型RFCRS采用LATCH系统安装时，其平均HIC15值最为恶劣：葛莱SnugRide®的HIC15值为394，宝得适Chaperone的HIC15值为133；而采用ELR腰肩式安全带安装时，葛莱SnugRide®的HIC15值为218，宝得适Chaperone的HIC15值为65；采用ALR腰肩式安全带安装时，葛莱SnugRide®的HIC15值为194，宝得适Chaperone的HIC15值为78。对于可双向安装的RFCRS（英孚乐Tribute®），不同安装方式对其HIC值未产生统计学意义上的显著差异。在多数试验中，ATD的头部均撞击了安装RFCRS的座椅靠背，此类头部撞击是本次试验中测得较高HIC15分值的主要原因。

研究结论：本研究结果表明，当与婴儿型RFCRS配合使用时，LATCH系统在后方碰撞工况下无法提供与腰肩式安全带相当的头部损伤防护效果。