UMHS LOGOUniversity of Michigan
Department of Pediatrics

Evidence-Based Pediatrics Web Site

Booster Seats Provide More Effective Injury Prevention than Seat Belts in Children Aged 4-7 Years Who Are Involved in a Motor Vehicle Collision


  • Do booster seats provide better protection from injury than seat belts in children between 40 and 80 pounds who are involved in a motor vehicle collision?

Clinical Bottom Lines

  1. Children aged 4-7 years who are restrained in booster seats have a lower odds of injury than those restrained in seat belts, with a NNT of 85.1
  2. Since motor vehicle collisions are the leading cause of injuries in this age group, counseling to increase booster seat usage can have a significant impact on child health.2

Summary of Key Evidence

  1. Cross sectional survey of child passengers involved in motor vehicle collisions reported to State Farm Insurance in 15 states between Dec 1998 and May 2002. The investigators examined types of restraint, seating position, driver age, medical treatment, and injury severity in 4-7 year old children.1
  2. Booster seat usage is low, ranging from 16% among 4 year olds to 4% among 6-7 year olds.
  3. Overall, the odds of injury were 61% lower in booster-seat restrained children than in seat-belted children (OR 0.39, 95% CI 0.20-0.77). Adjusting for various factors, including driver age and seating location, did not drastically alter these odds.
  4. The study demonstrated excellent validity in that it reflected real world use of child restraint systems. Investigators demonstrated a good measurement of agreement between survey responses and in-depth crash investigations. Sensitivity analysis supported survey responses.

Additional Comments

  • AAP recommendations: Children should use belt-positioning booster seats once they outgrow the car safety seat and until the adult seat belt fits properly. Generally, seat belts will fit when the child is at least 4'9" and between 8-12 years of age.3
  • Michigan law: Children aged 3 years and younger must be in a child safety seat.4
  • Many other states have passed laws requiring older children, up to age 9, to use a belt-positioning booster seat.5


  1. Durbin DR, Elliot MR, Winston FK. Belt-Positioning Booster Seats and Reduction in Risk of Injury Among Children in Vehicle Crashes. JAMA 2003; 289: 2835-2840.
  2. Centers for Disease Control and Prevention, National Center for Health Statistics. Health, United States, 2004. Accessed January 10, 2005.
  3. American Academy of Pediatrics. Car Safety Seats: A Guide for Families, 2004. Accessed January 10, 2005.
  4. State of Michigan. Excerpt of Michigan Vehicle Code. Accessed January 11, 2005.
  5. Advocates for Highway and Auto Safety. State booster seat law chart. Accessed January 11, 2005.

CAT Author: Marisa C. Louie, MD

CAT Appraisers: Alex Kemper, MD

Date appraised: January 12, 2005

Last updated November 28, 2006
Department of Pediatrics and Communicable Diseases
© 1998-2002 University of Michigan Health System