University of Michigan Transportation Research Institute, Ann Arbor, Michigan, USA.
Traffic Inj Prev. 2013;14(5):520-31. doi: 10.1080/15389588.2012.701030.
Lower anchors and tethers for children (LATCH) was intended to standardize the attachment between child restraints and vehicle seats. However, LATCH implementations vary, resulting in differences in ease of attachment of child restraint connectors. Identifying vehicle characteristics associated with correct child restraint installations can provide guidance for designing vehicle LATCH systems that increase correct child restraint installations.
The LATCH system and other relevant vehicle characteristics were documented in 98 top-selling 2010-2011 vehicles. These features, together with proposed LATCH usability recommendations from the International Organization for Standardization and Society of Automotive Engineers, were used to select 12 vehicles for volunteer testing with a range of LATCH system characteristics. Thirty-six volunteers were assigned to 4 groups; each group tested 3 vehicles, 4 child restraints (infant, rear-facing convertible, forward-facing convertible, and combination seat), and 2 installation methods (lower anchors and seat belt) in a split-plot experimental design. Mixed-effects logistic regression models were used to identify predictors of tight installation and correct lower anchor use.
Vehicle survey results indicated that most vehicle manufacturers provide the minimum number of LATCH hardware locations required by regulation. Among 21 vehicles with a third row, 4 had no tether anchors and 11 had no lower anchors in the third row. Study volunteers correctly used the lower anchors in 60 percent of LATCH installations and used the top tether in 48 percent of forward-facing installations. When the tether was used, use was correct in 46 percent of trials (22% of all forward-facing installations). Only 13 percent of all trials had completely correct child restraint installation (correct use of lower anchors or seat belt, correct tether anchor use, tight seat installation, and correct installation angle). Tight installation was 3.3 times as likely with correct lower anchor use compared to trials with incorrect use. Three lower anchor characteristics were associated with rates of correct lower anchor use above 50 percent: clearance angle around the lower anchors greater than 54°, attachment forces less than 178 N, and anchor depth within the seat bight of less than 2 cm. Vehicles meeting all 3 criteria were 19 times as likely to have lower anchors used correctly compared to vehicles meeting none of the criteria. No vehicle features predicted either use of tethers or correct use of tethers.
Vehicle LATCH systems that improve lower anchor accessibility could increase the rate of correct lower anchor use, but more research is needed to understand factors associated with tether use and correct use.
儿童用下固定锚和系绳（LATCH）旨在使儿童约束装置与车辆座椅之间的连接标准化。然而，LATCH 的实施方式存在差异，导致儿童约束装置连接件的连接易用性存在差异。确定与正确安装儿童约束装置相关的车辆特征，可以为设计增加正确儿童约束装置安装的车辆 LATCH 系统提供指导。
记录了 98 款畅销的 2010-2011 年车型的 LATCH 系统和其他相关车辆特征。这些特征，以及国际标准化组织和汽车工程师协会提出的 LATCH 易用性建议，被用于选择具有不同 LATCH 系统特征的 12 款车辆进行志愿者测试。36 名志愿者被分为 4 组；每组测试 3 辆车、4 种儿童约束装置（婴儿、后向可转换、前向可转换和组合座椅）以及 2 种安装方法（下固定锚和安全带），采用裂区实验设计。混合效应逻辑回归模型用于确定紧安装和正确使用下固定锚的预测因子。
车辆调查结果表明，大多数车辆制造商提供的 LATCH 硬件位置数量符合法规要求。在 21 款有第三排座椅的车辆中，有 4 款没有第三排的系绳锚，有 11 款没有第三排的下固定锚。研究志愿者在 60%的 LATCH 安装中正确使用了下固定锚，在 48%的前向安装中使用了顶系绳。当使用系绳时，在 46%的试验中使用正确（占所有前向安装的 22%）。只有 13%的试验完全正确安装了儿童约束装置（正确使用下固定锚或安全带、正确使用系绳锚、座椅安装牢固、正确安装角度）。正确使用下固定锚的试验比不正确使用下固定锚的试验发生紧安装的可能性高 3.3 倍。有 3 个下固定锚特征与超过 50%的正确使用下固定锚的比例有关：下固定锚周围的间隙角度大于 54°、连接力小于 178N 和锚在座椅弯角内的深度小于 2cm。符合所有 3 个标准的车辆正确使用下固定锚的可能性是不符合任何标准的车辆的 19 倍。没有车辆特征可以预测系绳的使用或正确使用系绳。
提高下固定锚可达性的车辆 LATCH 系统可以提高正确使用下固定锚的比例，但需要进一步研究了解与系绳使用和正确使用相关的因素。
