http://www.nhtsa.dot.gov/cars/testing/ncap/Index.cfm
What is the difference between a full frontal test and an offset crash test? Does NHTSA do both?
The NHTSA frontal crash test crashes the full width of the front of a vehicle into a rigid barrier. This maximizes the energy absorbed by the front of the vehicle so that the occupant compartment is more likely to remain intact. The full frontal tests produce high level occupant compartment decelerations, making them very demanding of the restraint systems, thus providing better information on the safety features and their performance.
In offset crash tests, like those performed by the Insurance Institute of Highway Safety (IIHS) http://www.iihs.org/, only one side of a vehicle's front end is hit, thus a smaller area of the structure absorbs the energy from the crash. Offset crashes are more demanding on the structure of a vehicle, and intrusion into the occupant compartment is more likely in these crashes. NHTSA does not currently perform the offset crash test.
The results from NHTSA’s full-width frontal crash and IIHS’ offset frontal crash test complement each other. They can be used together to assess overall frontal crash safety in terms of the effectiveness of restraint systems and the integrity of the occupant compartment.