Consumer usability of flexible vs. rigid lower anchor hardware in infant child restraint system (CRS) installations

Child restraint systems (CRS) can be installed using the Lower Anchors and Tethers for CHildren (LATCH) system. Two different types of lower anchors (LA) are available on CRS in the United States: (1) traditional flexible webbing LA, or (2) rigid LA, which is similar to the European ISOFIX system. The objective of this study is to evaluate consumer usability of flexible vs. rigid LA on infant CRS bases.

Thirty adult volunteers were recruited to install one infant CRS base with flexible LA and one infant CRS base with rigid LA into two different vehicles apiece, for a total of four installations per participant. One vehicle had easily accessible LA hardware and the other vehicle had less accessible LA hardware. A Child Passenger Safety Technician (CPST) inspected each installation and recorded any misuse or errors. Participants were asked to share their opinions and preferences on the two types of LA via written survey and verbal interview. Outcome variables include the number of errors committed, consumer preference, and ease of use (measured by time spent on each installation and participant feedback) of each LA system.

Rigid LA installations resulted in higher rates of correct installation compared to flexible LA (72% correct vs. 47% correct, χ2 = 7.761, p = 0.0053). Participants reported better physical ease-of-use and higher confidence with rigid LA compared to flexible (Likert scale with Wilcoxon signed rank test, two-tailed, for paired data: p = 0.0326 and p = 0.0023, respectively). Rigid LA was faster to install during users' second installation of each CRS compared to flexible (p = 0.0007) but was not faster during the first installation (p = 0.1165, matched-pair two-tailed t-tests). This indicates that each CRS required about the same amount of time for participants to familiarize themselves with the system, but once familiar, the rigid LA system was faster to install. Overall, 24/30 participants (80%) preferred rigid LA to flexible. Self-reported sociodemographic factors suggest that the participant sample was skewed toward highly-educated, white, native English speakers.

The rigid LA system was preferred by this group of consumers for installation of the base of infant CRS. The lower rate of installation errors suggests that rigid LA may help reduce the reported high rates of incorrect LA installation in vehicles in the US.