The recently released NHTSA study, "Roof Crush Analysis Using 1997-2001 NASS Case Review," which has been in the works for nearly four years, reviewed NASS rollover crashes in an effort to determine whether roof deformation patterns identified in an earlier agency study were still valid for current vehicle designs (see "Upgraded Rollover Roof Crush Protection: Rollover Test and NASS Case Analysis" NHTSA, June 1992). The new study, which examined 273 rollovers from 1997-2000 NASS, also examined the frequency of roof deformation patterns to determine if differences existed among various vehicle classes. Patterns were compared to results of 216 tests, tests with extended crush limits, SAE J996 drop tests, and the extent that windshields provided roof support.