When shopping for a car, you've no doubt compared crash-test ratings. Whether from the government or insurance industry, crash-test scores provide valuable insight into the occupant protection a car provides. But these ratings don't tell the whole story.

For instance, the front-crash scores simulate striking a same-sized vehicle. What happens if you hit a larger, heavier, or taller vehicle? Results from a new study being presented today by researchers at the University of Buffalo reveals the impact of your car-buying decision.

While the laws of physics dictate that in a crash between mismatched vehicles, the lighter one takes the brunt of the impact, this study shows just how unequal the contest is.

In car vs. SUV head-on crashes, the study found that the odds of death were 7.6 times higher for the car driver than the SUV driver. In crashes where the car had a better front crash-test rating than the SUV did, the car's driver fared a bit better but was still four and a half times more likely to die than the SUV driver. (Watch crash-test videos.)

The study looked at information from severe head-on crashes in the government-managed FARS (Fatality Analysis Reporting System) database. In particular, the authors were looking to see what role car-type played in the outcome and how reliably crash scores predicted survival. The data sample included 83,251 crashes. (To learn more about crash tests, read our primer "Crash test 101.")

The researchers concluded that at least for head-on crashes, the vehicle type is more important than the crash-test rating in predicting survival. It's correct that you can't assume that a good crash-test score is some sort of guarantee. But there is more to choosing a safe vehicle than simply picking a big one.

Front crashes account for about half of all passenger vehicle deaths on American roads, according to the Insurance Institute for Highway Safety. Based on its analysis, the Institute says overall "...a driver of a vehicle rated Good in the moderate [front] overlap test is 46 percent less likely to die in a frontal crash, compared with a driver of a vehicle rated Poor. A driver of a vehicle rated Acceptable or Marginal is 33 percent less likely to die than a driver of a poorly rated one." In other words, ratings do matter.

Choosing an SUV for safety isn't an automatic win, as their higher center of gravity makes them more prone to rollover, an often fatal event. Electronic stability control (ESC) substantially reduces rollover risk, and we highly recommend it when shopping for a used vehicle. ESC has been mandatory since the 2012 model year and was widespread for several years before then. It is telling that most of the 6,800 occupants killed in rollovers in 2010 were not wearing seat belts, suggesting that many of those deaths were easily preventable. (Learn more in "Rollover 101.")

How to choose a safe car

Just because a big, heavy vehicle has the advantage in a head-on with a smaller, lighter one, it doesn't mean that lighter vehicles are unsafe. In truth, they're safer than ever and overall traffic fatalities are near their all-time low. But do choose a vehicle with up-to-date safety equipment, such as antilock brakes, curtain air bags, and stability control. And choose one that has performed well in the various government and insurance industry crash tests. It should also have done well in the Consumer Reports' dynamic tests, such as accident avoidance and wet/dry braking. Even better than surviving a crash is avoiding one in the first place.

Safety considerations play an important role in Consumer Reports' criteria for recommending any car. A recommended vehicle also has to perform well overall in our more than 50 tests and have average or better predicted reliability, based on our annual survey of 1.2 million cars. (Check out our new and used car Ratings.)

After that, it is up to the driver to buckle up, stay sober and alert, and maintain a safe speed. That's the best way to maximize your odds of survival, no matter what size car you drive.

