A simple spring-mass model of the impact response of the side impact dummy (SID) is established. The spring and mass constants of the model are established through system identification methodology based on data from impact tests. The tests are performed in laboratory with hydraulically driven impactors impacting the chest and pelvis of the SID. The input data to the model consist of measured contact force or impactor velocity time histories, and the output data are accelerations on the rib, spine, and pelvis of the SID. The established model appears to predict the test results with reasonable accuracy.The main purpose of this study, however, is to use this simple model to carry out parametric studies of the response of the dummy with changing impact parameters, the result of which would be useful in understanding vehicle crash tests using the SID. The parameters studied here include the impactor velocity, padding force-deflection characteristics, padding thickness, and pelvis-chest impact timing offset. The results show that the dummy responses used in the Federal Motor Vehicle Safety Standards 214 (FMVSS214) have strong, and in some cases complex, dependence on these parameters. Furthermore, the results clearly show that the reason for the complexity lies in the fact that these measurements in essence are the transient responses of a spring-mass system.