Research reported Monday shows a drop in child car accident deaths , particularly among 6- and 7-year-olds, as most U.S. states have enacted laws requiring booster seats for children who have outgrown traditional carseats.

The booster seats position older children correctly so that seatbelts go across the shoulder (not the neck) and the lapbelt across the hips. The only states that do not have laws mandating the use of booster seats are Florida and South Dakota, but many states vary in the legal requirements.

In a new study, though, researchers found what Houston car accident lawyers have known for a while — fewer children ages 4 to 7 have died in auto accidents since these laws have been put into effect. Between 1999 and 2009, there was an 11 percent lower risk of child traffic deaths in states that required booster seats versus states with no requirement. In states that required the seats for children up to ages 6 and 7, the deaths dropped by about one-quarter versus the states with no boost seat requirement.

According the American Academy of Pediatrics, children should ride in carseats with a harness until 4 years of age or they have outgrown the seat. After this time, a booster seat should be used until they are between 8 and 12 years old, or reach 4-feet, 9-inches tall.