IIHS conducts its crash tests a little differently. For one, there's no star system. Instead, the agency ranks vehicles in one of four ways: Poor, Marginal, Acceptable and Good, with Good being the highest possible rating.
IIHS puts vehicles through five different crash tests. There's a small-overlap front test, where 25 percent of the car's frontal width strikes a barrier at 40 mph. There's a moderate-overlap front test, where a larger portion of the car strikes the barrier. There's a side test, where an SUV-like barrier hits cars at 31 mph. There's a roof-strength test, where a metal plate is pushed against a car's roof to determine whether it would easily collapse in a rollover, and there's a head-restraints-and-seats test, which measures forces on a driver's head and neck in a collision. IIHS has also recently started testing front-crash-prevention safety equipment, such as systems that avoid or alert drivers to an impending forward collision.