The Dodge Ram pickup has earned a top score in crash tests, reversing the "poor" rating of a previous model, an insurance industry research firm announced on March 20.The Insurance Institute for Highway Safety (IIHS) said three import cars had earned "good" ratings as well, while an import minivan was rated "acceptable."The institute tests vehicles by crashing them into a barrier at 40 miles per hour, with the vehicle positioned so that only the driver's side hits the barrier.The institute says it works to reduce insurance costs and publicizes the results of its tests to pressure automakers. The tactics appears to be working -- many auto manufacturers now specifically design vehicles to pass the tests, according to Reuters.The Ram, which was redesigned last year, matched the "good" grade of the previous topscorer, the Toyota Tundra pickup. The Chevrolet Silverado had been rated "marginal," while the Ford F-150 was rated "poor." The institute said the Subaru Impreza, Mitsubishi Lancer and Volvo V40 small cars also earned "good" ratings, while the Kia Sedona minivan was given an "acceptable" rating.