NEW YORK (CNN/Money) - In new crash tests by the Insurance Institute for Highway Safety, the 2004 Toyota Rav4 became the first vehicle to earn a double "Best Pick" rating: one for side-impact safety and one for frontal-crash safety. It earned that rating, however, only when equipped with optional side air bags.

"Results for (the Rav4) show manufacturers can provide good protection for occupants in the two most common kinds of serious crashes," said Adrian Lund, the Insurance Institute's chief operating officer.

The Institute also tested the newly redesigned 2005 Subaru Legacy. The Institute had included the 2004 Legacy in an earlier round of crash tests involving inexpensive mid-sized sedans, but tested the 2005 vehicle because it is substantially different from the earlier version.

The new Legacy earned the rating of "Marginal," the second-worst rating possible, for side-impact protection. It earned a "Best Pick" rating for frontal-impact protection.

The 2005 Legacy was actually tested twice for side-impact safety. The Institute's first side-impact test on the car revealed that the side airbag was folded in a way that prevented it from deploying quickly to protect occupants' heads. In early June, Subaru recalled all 2005 Legacy's to correct the problem and the car was retested by the Institute on May 18.

Although the crash test dummy's head was better protected in the second test, the test still revealed a high likelihood of rib fracture, internal organ injuries and the possibility of pelvic fractures, resulting in the car's "Marginal" rating.

2004 Toyota Rav4

The Rav4 had also been tested previously for both front- and side-impact safety. The 2003 Rav4 had earned the Institute's lowest rating of "Poor" in side-impact tests. After a 2001 redesign, the Rav4 had gotten an "Acceptable" rating in the Institute's frontal crash test.

Although it was not substantially redesigned, the 2004 Rav4 was retested because Toyota had made improvements to the vehicle's structure to better protect occupants in front and side crashes, said Russ Rader, a spokeperson for Insurance Institute. Also, side-air bags were added as a $680 option in newer Rav4 models.

The tests, conducted by the Insurance Institute for Highway Safety, emulate a more deadly type of crash than that modeled in the U.S. government's National Highway Traffic Safety Administration's side-impact crash tests. In the Insurance Institute tests, the car is struck in the side by 3,300 pound barrier designed to simulate the front of a pick-up truck or SUV. The barrier smashes into the car at a speed of 31 miles per hour.

2005 Subaru Legacy GT

In government side crash tests, the barrier is designed to simulate a car. Cars are lower to the ground than trucks or SUVs, so there is much less chance the impacting barrier will directly strike the heads of crash dummies. In real-world side crashes with trucks or SUVs, car occupants' heads can be struck by the higher vehicle's front end as it punches through the car's doors and side windows, according to the Insurance Institute.

The crash test dummies used in the Insurance Institute's tests are relatively small, designed to simulate a small woman or older child. As with a shorter person, the shorter crash dummies' heads are more likely to be struck directly by the force of the moving truck-like barrier.

The Institute's frontal crash test involves a 40 mile-per-hour crash into a deformable barrier. The IIHS test is an offset crash test, meaning that only one side of the vehicle's front end strikes the barrier. That way, crash forces are not evenly distributed across the front bumper but are concentrated on one side.