An Assessment of Injury for Pediatric Motor Vehicle Occupants with Premature or Delayed Graduation from Forward-facing to Booster Restraint

Principal Investigator: Caitlin Locey, BS, Children’s Hospital of Philadelphia

Below is an executive summary of this project. Please note that this summary describes results and interpretation that may not be final. Final interpretation of results will be in the peer-reviewed literature.


Several observational studies within the United States and internationally have revealed a trend of “premature graduation,” or children who were transitioned from forward-facing child restraint systems (FF CRS) to belt-positioning boosters (BPB) before reaching the recommended booster seat age or weight. The objective of this study was to perform an updated examination to evaluate injury risk for several age, height, and weight criteria for FF CRS and booster seated occupants to quantify the injury risk associated with prematurely graduating.

Using data from the National Automotive Sampling System – Crashworthiness Data System (NASS-CDS) for crash years 2002- 2012, the premature or delayed graduation of 1,478 child occupants was assessed. Injury risk (AIS2+) for “premature graduation” BPB occupants (i.e., small/young children in BPB) was compared to occupants of the same age, weight, or height in a FF CRS and appropriately aged and sized occupants in a BPB. Similarly, injury risk for “delayed graduation” FF CRS occupants (i.e. those who remained in their FF CRS beyond traditional transition ages or sizes) was compared to occupants of the same age, weight, or height in a BPB and appropriately aged and sized occupants in a FF CRS.

There were no detectable patterns in relative injury risk among the comparison groups. Those with delayed graduation (older/heavier children in FF CRS) appeared to have a slightly lower injury risk than those of comparable age or size in BPB; however, these differences were not statistically significant. Overall, the risk of injury was very low for all restraint conditions, indicating that CRS offer excellent protective benefit in the event of a crash.

In addition to the NASS analyses, detailed crash investigation information was gathered from the Crash Injury Research and Engineering Network (CIREN) database maintained by NHTSA. The CIREN database was queried for all AIS 2+ injured occupants using a FF CRS or BPB. Cases were defined as “premature graduation,” “delayed graduation,” or “age-and-size appropriate” users based on age, weight, and height criteria. Each case was retrospectively reviewed to determine injury causation scenarios for “premature graduation” BPB-seated occupants and “delayed graduation” FF CRS-seated occupants. Misuse for these cases was examined in detail. Misuse of the CRS for those who were restrained in FF CRS with delayed graduation (i.e., larger children in FF CRS) was critical to the injury causation.

This analysis provides insight into the issue of graduation between child restraint types, rather than graduation between a CRS and the vehicle lap and shoulder belt, which has previously been the focus of research. The findings ultimately can be used to educate consumers when deciding when to transition their children.

Project Team Members

Kristy Arbogast, PhD, Children’s Hospital of Philadelphia; Rachel Hammond, MS, Children’s Hospital of Philadelphia


Christine Evangelista, Elizabethtown College

IAB Mentors

Eric Dahle, Evenflo Company Inc.; Audrey Eagle, Chrysler Group LLC; Julie Kleinert, General Motors Holdings LLC; John Bachner, Graco Children’s Products Inc.; Rajiv Menon, Dorel Juvenile Group