Beth Milito and her husband bought a 2011 Toyota Sienna based on friends’ recommendations and the minivan’s overall four-star safety rating to protect their four children.

But tucked into the details of the government’s crash test results was another rating that Milito said she never saw, which now has her wondering about her own safety. The front passenger seat on Milito’s Sienna received two out of five stars on the frontal crash test, a fall from the top five-star rating for that seat on the Sienna’s 2010 and older models.

The key difference: Starting with 2011 models, the federal government replaced an average-size male dummy with a smaller female dummy for some tests.

When the 2011 Sienna was slammed into a barrier at 35 mph, the female dummy in the front passenger seat registered a 20 to 40 percent risk of being killed or seriously injured, according to the test data. The average for that class of vehicle is 15 percent.

“When we’re out and about as a family, I’m the one sitting in that seat,” said Milito, of Alexandria, Va., after learning of the test results.

And she doesn’t know how the female dummy would fare behind the wheel, where she spends most of her car time commuting and ferrying kids. The star-rating system’s frontal crash test uses only the male dummy in the driver’s seat.

Consumer advocates say the female dummy’s subpar performance in some top-selling vehicles reveals a need to better study women and smaller people in collisions. Over three decades of government testing aimed at helping car buyers choose between vehicles, only male dummies were used until recently. The female dummy also mimics a 12-year-old child.

Why it matters

In general, experts say, the smaller the person, the fewer crash forces the body can tolerate. When cars wrap around trees or utility poles, for example, smaller drivers and passengers suffer more head, abdominal and pelvic injuries but fewer chest injuries than average-size people, according to the National Highway Traffic Safety Administration. Women’s less muscular necks also make them more susceptible to whiplash, researchers say.

A 2011 study by the University of Virginia’s Center for Applied Biomechanics found that seat-belted female drivers in actual crashes had a 47 percent higher chance of serious injuries than belted male drivers in comparable collisions. For moderate injuries, that difference rose to 71 percent.

Auto safety watchdog groups say they’ve been pushing the NHTSA to go beyond the average-sized male dummy since the agency launched the star-rating system in 1978. They say those tests should take into account not only women but the increasing elderly and obese populations and larger children who have outgrown child safety seats. The tests, they say, also miss average women who fall between the 50th percentile male dummy, which stands 5-feet-9 and 172 pounds, and the unusually petite female dummy, which is 4-feet-11 and 108 pounds.

The average American man is 5-9 and 195 pounds, and the average American woman is 5-4 and 165 pounds, according to Centers for Disease Control and Prevention statistics.

Child dummies, which are not included in the star-rating system, are used in separate tests of air bags and child safety seats.

“A lot of women do substantial (safety) research before going to buy a car,” said Joan Claybrook, a longtime consumer advocate who was head of the NHTSA during the Carter administration, when the star-rating system was introduced. “Yet there’s not a whole lot of information about how cars impact women” in collisions.

Greater risk

Government data from police-reported crashes also show women are at greater risk of being hurt, particularly when they’re not behind the wheel. In the driver’s seat, men outnumber women by a ratio of 3 to 1 in vehicle fatalities. Men also drive 50 percent more than women — an average additional 5,000 miles annually.

While females comprise one-quarter of all driver fatalities, they make up half of all passengers killed, according to the NHTSA. Because they’re on the road less, women are killed and injured at disproportionately higher rates than males, experts say.

The relative safety shortcomings in the front passenger seat for the female dummy went beyond the 2011 Sienna and its 2012 model, which improved to three stars for that seat. Other top-selling vehicles that earned three stars for that seat include the 2011 Honda CR-V, the 2012 Nissan Sentra and the 2012 Ford Fusion. The 2012 Acura TL received two stars for that seat.

NHTSA officials say they’ve used the female dummy in federal compliance crash tests since 2003, mostly to ensure the safety of air bags. Early versions of air bags severely injured or killed some smaller women and children.

However, those compliance tests gauge only whether a vehicle meets the government’s minimum safety standards. Consumers can’t readily see those results, and it’s the star-rating tests that reveal how one vehicle’s crash protections compare to another. The star ratings — which can be found at www.safercar.gov and appear on new car window stickers — use the car-buying market to encourage automakers to voluntarily exceed the minimum standards.

NHTSA officials said they recently included the female dummy in the frontal crash test as one of several changes to make the star-rating tests more rigorous. Even when not required in government tests, auto manufacturers have long used different dummies — including the female dummy and a larger 95th percentile male dummy — in internal tests.