Discordance between age- and size-based criteria of child passenger restraint appropriateness

ABSTRACT

Objectives: In this study, we sought to accomplish the following objectives: to (1) calculate the percentage of children considered appropriately restrained across 8 criteria of increasing restrictiveness; (2) examine agreement between age- and size-based appropriateness criteria; (3) assess for changes in the percentage of children considered appropriately restrained by the 8 criteria between 2011 (shortly after updates to U.S. guidelines) and 2015.

Methods: Data from 2 cross-sectional surveys of 928 parents of children younger than 12 years old (n = 591 in 2011, n = 337 in 2015) were analyzed in 2017. Child age, weight, and height were measured at an emergency department visit and used to determine whether the parent-reported child passenger restraint was considered appropriate according to 8 criteria. Age-based criteria were derived from Michigan law and U.S. guidelines. Weight, height, and size-based criteria were derived from typical restraints available in the United States in 2007 and 2011. The percentage appropriate restraint use was calculated for each criterion. The kappa statistic was used to measure agreement between criteria. Change in appropriateness from 2011 to 2015 was assessed with chi-square statistics.

Results: Percentage appropriate restraint use varied from a low of 19% for higher weight limits in 2011 to a high of 91% for Michigan law in 2015. Agreement between criteria was slight to moderate. The lowest kappa was for Michigan law and higher weight limits in 2011 (κ = 0.06) and highest for U.S. guidelines and lower weight limits in 2011 (κ = 0.60). Percentage appropriate restraint use was higher in 2015 than 2011 for the following criteria: U.S. guidelines (74 vs. 58%, P < .001), lower weight (57 vs. 47%, P = .005), higher weight (25 vs. 19%, P = .03), greater height (39 vs. 26%, P < .001), and greater size (42 vs. 30%, P = .001).

Conclusions: The percentage of children considered to be using an appropriate restraint varied substantially across criteria. Aligning the definition of appropriate restraint use with current U.S. guidelines would increase consistency in reporting results from studies of child passenger safety in the United States. Potential explanations for the increased percentage of children considered appropriately restrained between 2011 and 2015 include adoption of the updated U.S. guidelines and the use of child passenger restraints with higher weight and height limits.

KEYWORDS:

• Child restraints
• child safety
• child seat
• children
• booster seat
• infant seat
• seat belt laws

Acknowledgments

The authors appreciate the contributions of the research assistants who recruited subjects and collected data. The authors are also grateful to the patients and families and the ED staff at both the C.S. Mott Children's Hospital and Hurley Medical Center who made this research possible. Data collection in 2011–2012 was supported by a grant from the Michigan Center for Advancing Safe Transportation Throughout the Lifespan.

Additional information

Funding

Data collection in 2015 was supported by a grant to Dr. Macy from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Grant K23 HD070913) funded by the National Institutes of Health (NIH). The content of this article is solely the responsibility of the authors and does not necessarily represents the official views of the National Institutes of Health. Data collection in 2011 was supported by a grant from the Michigan Center for Advancing Safe Transportation throughout the Lifespan (MCASTL).