Equivalent half sine approximations derived from accelerometer data for Federal Motor Vehicle Safety Standard (FMVSS) 208 dynamic compliance testing and other substantially similar non-FMVSS, non-New Car Assessment Program (NCAP) tests were characterized in terms of amplitude, circular frequency, time duration and displacement. The results were compared and contrasted with the idealized and actualized FMVSS 208 sled deceleration pulses. A total of 346 dynamic tests and 83 sled tests were considered. For the passenger vehicle subset of the FMVSS 208 dynamic test population these parameters were 224.98 ± 30.39 m/sec2, 34.11 ± 4.57 sec-1, 94 ± 13 msec and 0.619 ± 0.089 meters respectively. For the multipurpose vehicle subset of the FMVSS 208 dynamic test population theses parameters were 246.17 ± 43.61 m/sec2, 37.78 ± 6.38 sec-1, 86 ± 15 msec and 0.557 ± 0.100 meters respectively. The differences in all parameters between the two classifications were significant (p < 0.00004). For the dynamic frontal impact population en toto the valuations of these parameters for the passenger vehicle classification were 225.10 ± 29.07 m/sec2, 34.26 ± 4.26 sec-1, 93 ± 12 msec and 0.612 ± 0.085 meters respectively whereas for the multipurpose vehicle classification they were 243.82 ± 43.37 m/sec2, 37.50 ± 6.28 sec-1, 86 ± 15 msec and 0.560 ± 0.102 meters respectively. The differences in all parameters between the two classifications were significant (p < 0.0001). The corresponding parameters for the target half sine deceleration pulse of the FMVSS 208 sled test are 168.73 m/sec2, 25.12 sec-1, 125 msec and 0.839 meters. The sled half sine deceleration pulse substantially underestimates the characteristic mean response obtained from the half sine equivalents of dynamic tests.