Insurance Institute for Highway Safety
The IIHS uses five tests. They do two frontal tests. A small-overlap is set up with 25% of the front of the car hitting a barrier at 40 mph. A moderate overlap test allows more of the front of the car to hit the barrier. In a side-impact test a movable barrier hits the car side at 31 mph. A roof test involves a flat piece of metal pushed down against the roof to see at what point it collapsed. It is not an actual roll-over test. The last test is on the seats and head restraints. The IIHS classifies its rankings as Poor, Marginal, Acceptable or Good.