a child without a booster or a car seat will easily fly out of the seat belt. We are talking about a toddler. Granted, mine was on a bigger side, but he was 34# and 37" tall at 2, and 40# and 40" tall at 3 years and 4 months. A seat belt alone will not hold him in an accident, hence, the child is considered unrestrained. You are comparing a 3 year old to an adult sized person....