Women get in fewer car accidents than men. But when they do, they're up to 73% more likely to be injured and 28% more likely to die, according to new data from the Insurance Institute for Highway Safety (IIHS).

One reason for that might be there is no crash test dummy that represents the average female body used in car safety testing, despite women making up more than half of the licensed drivers in the United States.

"It's completely unacceptable," said Jason Levine, executive director of the Center for Auto Safety. "What we're seeing in the studies that keep coming out is that the crash protection is not equal, and it should be."

Advocates are renewing calls for federal regulators to advance studies of crash impacts on women after several reports have shown women are significantly more likely to be hurt in crashes.

More data — and updates to federal regulations — are necessary to help build better crash test dummies and models to increase vehicle safety, experts say.

Carla Bailo, CEO of the Center for Automotive Research, said the reason there is no average-size female dummy can be traced to "bad history."

"It's got to do with the fact that women didn't drive for a long time, and once they started, it was assumed incorrectly that it was just short trips to the store" and similar errands, she said.

The dummies are put through simulated crashes to find out whether a vehicle meets federal vehicle safety standards and in determining the vehicle's federal safety rating. Safety experts have known for decades that female and male bodies are affected differently by car crashes. But the National Highway Traffic Safety Administration (NHTSA) didn't start using a female-style dummy until 2003.

The dummy represents the fifth percentile of women in the 1970s, meaning 95% of women were larger than it. It is 4 feet 11 inches and weighs 108 pounds — smaller, by today's standards, than the average 12-year-old girl. The average American woman is just under 5 feet 4 and weighs around 171 pounds, according to the Centers for Disease Control and Prevention.

The male dummy, representing the 50th percentile of men in the 1970s, is the same height as the average man of today but is around 15% lighter. The female dummy is 8% shorter and 45% lighter.

The dummy also is not built like female bodies. Rather, it's a scaled-down version of its male counterpart, despite women and men having different spinal alignment, muscle strength and responses to trauma, Stanford University researchers say.

In an e-mail, agency spokeswoman Lucia Sanchez said, "NHTSA is working to develop crash simulation and human body models to represent a wide range of occupant size, sex and ages." She said the agency is funding research for computer models that might better represent all types of bodies.

A study from the University of Virginia showing significant injury disparities between men and women prompted U.S. Reps. Kathy Cantor (D-Fla.) and Jan Schakowsky (D-Ill.) to reach out to the NHTSA and ask what it's doing to address it.

In a response letter, Acting Administrator James Owens said previous NHTSA studies had shown that "differences in crash injury and fatality rates between men and women were not statistically significant." He added that the agency will continue evaluating crash data and developing "state-of-the-art tools" to evaluate injury causes in different body types.

His answer didn't cut it, Cantor said.

"We really need some answers. They just kind of glossed over that," she said. "A more comprehensive answer … would help us get to: Do we need to push to provide additional carrot or stick from the federal level to ensure NHTSA really is using all the tools at their disposal to ensure that everyone is safe?"

The types of injuries women suffered — disproportionately more leg injuries — indicate that regulators and researchers should invest in learning more about how women's bodies react to crashes, said Jessica Jermakian, vice president for vehicle research at the IIHS and one of the authors of the study.

"We need to understand why there is a difference in injury risk before we can identify what the solution is," Jermakian said.