Over 3000 fatalities and over 7000 serious head injuries result each year from occupants' heads striking various upper interior structures. The magnitude of this problem has prompted both government and industry to address the issue of reducing head injuries due to contact with these structures.

In a research project conducted by the National Highway Traffic Safety Administration (NHTSA) at the Vehicle Research and Test Center (VRTC), a component test approach was selected to evaluate the head injury causing potential of vehicle upper interior structures. Specifically, we chose a free-motion headform (FMH). The FMH can simulate the glancing and nonperpendicular head impacts experienced in real world accidents, and can measure head rotational motion.

For the purpose of validating the FMH results, 22 different head impact configurations were tested in 25 separate HYGE sled tests, using a full Hybrid III dummy. Also, 34 FMH tests were conducted under these same 22 configurations. A regression analysis indicated the HIC response of a full Hybrid III dummy in a sled test can be estimated from the results of a similar FMH test.

FMH impact tests were conducted on the upper interior structures of twelve cars, which were selected to be representative of the passenger car fleet on U.S. roadways. An impact speed of 20 mph (32 kph) was used to test the A-pillars and front headers of these vehicles, while 15 mph (24 kph) was used on the side roof rails and B-pillars. HIC, peak resultant linear acceleration, and peak resultant rotational acceleration were measured in each test. In addition, the force/deflection characteristics of each structure were measured using a guided, rigid impactor.