Dennis Durbin has spent the last half-decade combing through data on thousands of car crashes, and the injuries suffered by children in those accidents. In recent years, one trend in particular began to catch his eye.

The number of SUVs on the road was steadily increasing—as was the number of children injured in crashes involving SUVs.

“It looked like families were increasingly choosing SUVs over smaller passenger cars,” says Durbin, an assistant professor of pediatrics and epidemiology at the University of Pennsylvania School of Medicine and a pediatric emergency medicine physician and clinical epidemiologist at Children’s Hospital of Philadelphia.

“We wanted to find out what the specific experience of children in these two kinds of cars was,” says Durbin, who is also a co-principal investigator at the Partners for Child Passenger Safety.

What Durbin and his colleagues turned up contradicts the popularly held belief among many parents that large SUVs are safer than smaller cars. After studying more than 3,900 children injured in either passenger cars or SUVs, the team found that SUVs do not provide a safer ride for children than passenger cars. That’s because the one advantage of SUVs—their size and weight—is offset by their tendency to roll over during an accident. Some research indicates SUVs are four times more likely to roll over than passenger cars, and though this tendency has long been known, it doesn’t appear that buyers are taking that into account.

“What we were simply trying to do is question the assumption that we believe many people have: That if they choose an SUV, their family will be safer,” Durbin says. “We’re not saying that SUVs are bad for families. We’re not saying that they are dangerous for children. But that assumption is simply not true. We want families to look beyond just the size and weight of the vehicles when choosing the right car for their families.”

Apart from its findings on SUVs, the research also showed that children who were not properly restrained in a car seat, booster seat or seatbelt during an SUV rollover were 25 times more likely to suffer injury than properly restrained children. Forty-one percent of unrestrained children in those crashes suffered serious injury—compared to just 3 percent of restrained children.

The SUV study is just the latest research to emerge from Partners for Child Passenger Safety, a research collaboration between Children’s Hospital of Philadelphia, Penn and State Farm Insurance. The program was created in 1998 to find out why car crashes remain the leading cause of death and disability in children over the age of 1 in the U.S. Since its launch, researchers there have published numerous reports and compiled a database covering more than 377,000 crashes involving 557,000 children. Today, the program is the largest study of children and car crashes in the world.

“I’m a pediatric emergency physician and a father of three kids,” Durbin says. “I think my interest in this area came about because of a combination of my own experience as a parent … and seeing what I see in the emergency department. It was clear that some children’s injuries could have been avoided. When [center lead investigator] Flaura Winston and I started comparing notes on this, we found the current government sources of information weren’t large enough with respect to children.”

At any one time, the center is working on a dozen or so different studies and currently, Durbin says, he is preparing a follow-up to the SUV study that will compare the safety of those vehicles to minivans, which some data suggests combine the size and weight advantages of SUVs with a greatly reduced tendency to flip. The center is also hoping to investigate whether newer models of SUVs are less likely to roll over, as some manufacturers claim.

In the meantime, Durbin hopes parents will take heed of the central message of his SUV research.

“Since you can’t predict what kind of crash you’re going to be in,” Durbin says, “or if you’re going to be in a crash at all, the single most important thing families can do is restrain your children properly, for their age, in the backseat of the vehicle for every trip, regardless of what kind of vehicle you drive.”