Child seat belt guidelines: Examining the 4 feet 9 inches rule as the standard

J Trauma Acute Care Surg. 2017 Aug;83(2):305-309. doi: 10.1097/TA.0000000000001543.


Background: Current American Academy of Pediatrics recommendations regarding transition from child safety/booster seat to adult safety belt use indicate that children should be at least 4 feet 9 inches, 8 years old, or 80 pounds. Proper fit in the vehicle seat, assessed with a five-point fit test, should also be met. Although most children reach 4 feet 9 inches around age 8 years, each child and vehicle presents a unique combination; thus a child may not fit appropriately in all vehicle types using only the 4 feet 9 inches requirement.

Methods: We enrolled children, aged 7 years to 12 years, into our study. Height, weight, and demographic data were obtained. A Child Passenger Safety Technician then performed the five-point fit test in each of a uniform lineup of five vehicles. Data were collected on fit in the standard vehicle seat and also in a booster seat. We set 90% as the threshold proportion of children who meet all criteria for proper fit to validate current recommendations of a height of 4 feet 9 inches.

Results: Data were collected on 388 children. The percentage of 90% proper fit was met in the compact car and small sport-utility vehicle (SUV). However, only 80 (77%) of 104 students (p < 0.0001) that were 4 feet 9 inches or higher fit properly in the large SUV, only 87 (83%) of 105 students (p = 0.02) fit properly in the pickup truck, and only 91 (89%) of 102 students (p = 0.74) fit properly in the minivan.

Conclusion: Substantial proportions of children meeting current height guidelines for an adult seat belt do not meet safety requirements for fit, especially in larger, commonly used vehicles (large SUVs and trucks). This emphasizes the need for evaluation of fit by a trained personnel and/or development of standard back seat dimensions in all vehicles for maximum safety.

Level of evidence: Epidemiologic study, level III; Therapeutic study, level V.

Publication types

  • Comparative Study

MeSH terms

  • Age Factors
  • Automobiles / standards
  • Body Height*
  • Body Weight*
  • Child
  • Child Restraint Systems / standards*
  • Female
  • Guideline Adherence*
  • Humans
  • Male
  • Prospective Studies
  • Safety*
  • Seat Belts / standards*