More than one-third of children under 13 years old who died in car crashes in 2011 were not buckled in or not in car seats, new U.S. data shows.

Vehicle collisions are one of the leading causes of death for children, National Highway Traffic Safety Administration research shows; they killed close to two children every day in the U.S. in 2011, and injured 338 others.

As many as one in three of these deaths involved children who were not properly secured in a child car seat or not buckled in, the NHTSA says.

More than twice as many of these unrestrained children fatalities involved children in SUVs collisions as opposed to children in cars; the number of fatal unrestrained-child vehicle collisions was also higher for pickup trucks and vans.

The NHTSA says that child restraints saved the lives of more than 260 children under five years old in 2011.

A recent study publicized by General Motors found that one in four parents worldwide admit to not making sure their children are safely secured in the vehicle before heading out on the road.

NHTSA data also shows less than one-half of parents who think they have their child in the right car seat actually do.

Check out our child car seat selection guide for more information on picking the right seat for your child, and for more resources.

(NHTSA via AutoBlog)