PHILADELPHIA -- Children appear to be safer when driven in a car by a grandparent instead of a parent, the Wall Street Journal reported in its Tuesday edition, citing details from a new study.

The young were half as likely to be injured in a crash when a grandparent was behind the wheel compared with crashes involving a mother or father. The lower injury rate was surprising to researchers because older drivers are more likely to be involved in an accident than younger drivers, and grandparents were shown to be slightly less likely than parents to properly use restraints such as car seats or booster seats.

The study, led by researchers at Children's Hospital of Philadelphia, is believed to be the first comparing parent and grandparent drivers. It was published online Monday in the journal Pediatrics.

The researchers looked at insurance-claims data from State Farm Mutual Automobile Insurance Co. involving children in 15 states and the District of Columbia from 2003 to 2007. They parsed the injury rates in crashes of cars with occupants age 15 and younger, and determined whether a grandparent or parent was driving, the severity of the crash and the use of seat belts and car seats.

A parent was driving in about 90 percent of the crashes and a grandparent in 10 percent. Yet grandparents accounted for just 6.6 percent of the total injuries in the study, and the parents the rest.

The injury rate, calculated per 100 child occupants, was 0.7 percent for grandparents and 1.05 percent for parents.

"There's something about the grandparents that they are driving more cautiously," says Flaura Winston, one of the researchers. The study suggests grandparents perhaps are more nervous about driving such "precious cargo" and drive more cautiously to offset the extra risks older drivers face.