Parents should put infants and toddlers in the back seat in rear-facing car seats as long as possible, at least until they’re around 2, according to the American Academy of Pediatrics.

Drivers who don’t wear seat belts are more likely to skip seatbelts and car seats for their kids, an analysis of U.S. crash data suggests.

When the driver in a crash wasn’t wearing a seatbelt, young passengers up to age 15 were 16 times more likely to also be unrestrained than when drivers were buckled up, the study found. And when drivers went without seatbelts, passengers ages 16 to 19 were about 53 times more likely to be unrestrained.

“Often times, young passengers do not and cannot make the decision to be properly restrained — it is the driver’s responsibility,” said lead study author Douglas Roehler of Rush University Medical Center in Chicago.

“If the driver in a crash with a child passenger is not making the safe decision for themselves, we found that they were less likely to make safe decisions for their young passengers,” Roehler said by email.

Parents should put infants and toddlers in the back seat in rear-facing car seats as long as possible, at least until they’re around 2 years old or too large or heavy to fit in that position, according to the American Academy of Pediatrics (AAP).

After that, children should remain in the back of vehicles in front-facing car seats as long as possible, until they reach the weight and height limits for the seats. Many seats can work until kids weigh about 65 pounds.

When children can no longer use car seats, they should switch to booster seats until the vehicle’s lap and shoulder belt fit properly, which may happen when children are at least 4 feet 9 inches tall and 8 to 12 years old, according to the AAP.

For the study, researchers examined nationwide data on fatal and nonfatal crashes involving passengers 19 and younger from 2011 to 2015.

In a sample of all crashes during this period involving a fatality with a child passenger present, 32 percent of children up to age 8 died, 34 percent of 9- to 15-year-old passengers died and 40 percent of 16- to 19-year-olds died.

At the national level, the researchers calculate, about 25 in every 1,000 kids 8 and younger were killed as unrestrained passengers in motor vehicle crashes, as were 42 in every 1,000 youth 9 to 15 years old and 38 in every 1,000 teens 16 to 19.

In both fatal and nonfatal crashes, boys made up more than half of the unrestrained young passengers 15 and under, but girls made up the majority of unrestrained passengers in crashes involving older teens in the study.

One limitation of the study is that researchers lacked data on the type of restraints used by passengers, making it impossible to know if infants were properly placed in back seats in rear-facing seats or if the oldest teens who did use seatbelts used both the lap and shoulder belts.

The study also only looked at fatal crashes and nonfatal collisions requiring tow trucks, leaving out less-severe crashes.