Some popular small SUVs that were tested to see how well their roofs are likely to hold up during a rollover crash received "marginal" ratings.

More than 10,000 people are killed in rollover accidents every year, and SUVs and pickup trucks are the most rollover-prone vehicles. The Insurance Institute for Highway Safety recently conducted roof-strength tests to simulate what happens when a small SUV rolls over.

“When the roof caves in, you have less space to survive as the vehicle is rolling, and the other thing that is happening is that the windows and the windshield are cracking and breaking out, so there is greater likelihood that you can be ejected in that crash,” said Russ Rader, with the Insurance Institute for Highway Safety.

The institute has conducted side-impact, rear-impact and front-crash tests for some time. However, roof tests are new, and small SUVs were the first vehicles tested. The institute uses a rating system of good, acceptable, marginal or poor.

Of the12 small SUVs tested, the KIA Sportage had the weakest roof. In response, KIA says the roof test alone was "not a complete assessment of a vehicle's ability to protect occupants." The automaker points to its strong performance in other crash tests and says its vehicles "meet or exceed" federal safety standards.

The Honda CR-V, Ford Escape, Mazda Tribute and Mercury Mariner were rated "marginal."

The top performer was the Volkswagen Tiguan. With 15,000 pounds of pressure, its roof crushed in only about 2 inches. The Subaru Forester, Honda Element and Jeep Patriot also scored "good."