Belt fit for children in vehicle seats with and without belt-positioning boosters

Traffic Inj Prev. 2022;23(8):488-493. doi: 10.1080/15389588.2022.2112676. Epub 2022 Aug 26.


Objective: The purpose of the current study is to use 3D technology to measure in-vehicle belt fit both with and without booster seats across different vehicles among a large, diverse sample of children and to compare belt fit with and without a booster.

Methods: Lap and shoulder belt fit were measured for 108 children ages 6-12 years sitting in the second-row, outboard seats of three vehicles from October 2017 to March 2018. Each child was measured with no booster, a backless booster, and a high-back (HB) booster in three different vehicles. Alternative high-back (HB HW) and backless boosters that could accommodate higher weights were used for children who were too large to fit in the standard boosters. Lap and torso belt scores were computed based on the belt location relative to skeletal landmarks.

Results: Both lap and torso belt fit scores were significantly different across vehicles when using the vehicle belt alone (no booster). In all vehicles, lap belt fit improved when using boosters compared with no booster among children ages 6-12 years in rear seats-with one exception of the HB HW booster in the minivan. Torso belt fit improved when using boosters compared with no booster in the sedan, and torso belt fit improved in the minivan and SUV with the use of HB and HB HW boosters when compared with no booster.

Conclusions: Lap and torso belt fit for children ages 6-12 years in rear seats was substantially improved by using boosters. Parents and caregivers should continue to have their children use booster seats until vehicle seat belts fit properly which likely does not occur until children are 9-12 years old. Decision makers can consider strengthening child passenger restraint laws with booster seat provisions that require children who have outgrown car seats to use booster seats until at least age 9 to improve belt fit and reduce crash injuries and deaths.

Keywords: Booster seat; belt fit; premature graduation; transition to seat belt.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Accidents, Traffic*
  • Child
  • Humans
  • Infant Equipment*
  • Parents
  • Seat Belts
  • Technology