This study compared modern vehicle and booster geometries with relevant child
anthropometries. Vehicle geometries (seat length, seat pan height, shoulder belt
outlet height, and roof height) were obtained for 275 center and outboard rear
seating positions of US vehicles (MY 2009–2022). Measurements of 85 US boosters
(pan height and pan length) and anthropometries of 80 US children between 4–14yo
(seated height, thigh length, leg length, and seated shoulder height) were also
collected. Comparisons were made between vehicles, boosters, and child
anthropometries. Average vehicle seat lengths exceeded child thigh lengths
(+9.5cm). Only 16.4% of seating positions had seat lengths less than the child
thigh length mean+1SD. Even for children at least 145cm, only 18.8% had thigh
lengths greater than the average vehicle seat length. Child thigh lengths were
more comparable with average booster seat pan lengths for all multi-mode and
high-back designs (-2.0cm) and low-back boosters (+3.1cm). The average observed
booster pan height (9.9cm) would help most children achieve seated shoulder
heights similar to the Hybrid III 5th percentile Female ATD. Compared to vehicle
seats, booster geometries were more compatible with child thigh lengths and
assist children in achieving seated shoulder heights more comparable to the
vehicle restraint system. This emphasizes the continued need for shorter vehicle
seat cushion lengths for these occupants and the need to educate caregivers and
promote booster recommendations which highlight the importance of achieving
proper belt fit and avoiding slouched postures, even for children greater than 8
years and/or 145cm.
