About IIHS

The Institute's frontal crashworthiness evaluations are based on results of 40 mph frontal offset crash tests. Each vehicle's overall evaluation is based on measurements of intrusion into the occupant compartment, injury measures recorded on a 50th percentile male Hybrid III dummy in the driver seat, and analysis of slow-motion film to assess how well the restraint system controlled dummy movement during the test.

Building on its long-running vehicle ratings program for consumer information, IIHS introduced the small overlap test in 2012 to further improve occupant protection in frontal crashes. Most automakers design their vehicles for good performance in the IIHS moderate overlap frontal test and the federal government's full-width frontal test, but many haven't addressed the problem of small overlap crashes. In a 2009 IIHS study of vehicles with good ratings for frontal crash protection, small overlap crashes  accounted for nearly a quarter of the frontal crashes involving serious or fatal injury to front seat occupants.

The small overlap test is a demanding crash that replicates what happens when the front corner of a car collides with another vehicle or an object like a tree or utility pole. In the test, 25 percent of a car's front end on the driver side strikes a 5-foot-tall rigid barrier at 40 mph.

Side evaluations are based on performance in a crash test in which the side of a vehicle is struck by a barrier moving at 31 mph. The barrier represents the front end of a pickup or SUV. Ratings reflect injury measures recorded on 2-instrumented SID-IIs dummies representing a small (5th percentile) woman, assessment of head protection countermeasures, and the vehicle's structural performance during the impact.

Rear crash protection is rated according to a two-step procedure. Starting points for the ratings are measurements of head restraint geometry -- the height of a restraint and its horizontal distance behind the back of the head of an average size man. Seat/head restraints with good or acceptable geometry are tested dynamically using a dummy that measures forces on the neck. This test simulates a collision in which a stationary vehicle is struck in the rear at 20 mph. Seats without good or acceptable geometry are rated poor overall because they can't be positioned to protect many people.

In the roof strength test, a metal plate is pushed against 1 side of a roof at a constant speed. To earn a good rating for rollover protection, the roof must withstand a force of 4 times the vehicle's weight before reaching 5 inches of crush. This is called a strength-to-weight ratio. For an acceptable rating, the minimum required strength-to-weight ratio is 3.25. A marginal rating value is 2.5. Anything lower than that is rated poor.