NEW YORK (CNN/Money) - Of eight midsized sedans tested for side impact protection, four earned the Insurance Institute for Highway Safety's top rating of "good."

While none of the cars earned the worst rating, "poor," the Jaguar X-type received a rating of "marginal," the second-worst of four possible ratings.

The 2004 Saab 9-3, the Acura TL and the 2005 Mitsubishi Galant all received a rating of "good." The 2004 Saab 9-5 and the 2005 Mercedes C class and Volvo S40 earned ratings of "acceptable," the second-best rating.

The 9-3 is the first car to earn the Institute's "double best pick" rating. It was noted as a Best Pick in these most recent side impact test, and had previously earned a Best Pick in frontal crash tests.

"Earning a 'double best pick' is a rare achievement," says Institute chief operating officer Adrian Lund. "The only other vehicle to have done this is the Toyota RAV4, a small SUV, and then only when it was equipped with optional side airbags."

The Institute didn't test 11 other midsize inexpensive to luxury car models, because their manufacturers are making design changes to improve side impact performance. The Institute plans to test those models in the near future.

All of the eight cars in this round of tests have head-protecting side airbags as standard equipment. The 9-3 has side curtain airbags that deploy from the roof, as well as airbags that deploy from the car's front seats to protect occupant's chests.

"The curtain airbag did a good job of cushioning the heads of both the driver and rear passenger dummies," Lund says. "Plus, injury measures recorded on the neck, torso, pelvis, and left leg of the dummies all were low. Saab can still make improvements to the 9-3's structure, but in all other areas this was very good performance."

Insurance Institute ratings Frontal and side impact ratings for eight low-to-moderately priced midsized sedans on which the Institute has just announced side impact ratings Sedan Front impact rating Side impact rating 2004 Saab 9-3 Good (Best Pick) Good (Best Pick) 2004 Acura TL Good (Best Pick) Good 2004 Lexus ES 330 Good (Best Pick) Good 2005 Mitsubishi Galant Good Good 2004 Saab 9-5 Good (Best Pick) Acceptable 2005 Mercedes C class Good (Best Pick) Acceptable Volvo S40 Good (Best Pick) Acceptable Jaguar X-Type Good (Best Pick) Marginal

In the Institute's side impact test, a moving deformable barrier strikes the driver side of a passenger vehicle at 31 mph. The barrier weighs 3,300 pounds and has a front end shaped to simulate the front end of a typical pickup or SUV. In each side-struck vehicle are two instrumented dummies the size of a short woman, one positioned in the driver seat and one in the rear seat behind the driver.