In this study, acceleration signals measured from the SAE J577 mechanical shock machine are investigated in detail. The aim of this investigation is to derive representative standard acceleration signals to be used as acceleration loads for finite element fatigue analysis of Automotive Lighting parts. These signals can also be used as load inputs for vibration shakers which have the capability of driving time domain signals. First of all, acceleration signals have been measured from the free machine table and by the help of the signal analysis software, automatic averaging operation has been performed from the long train of shock signals to have a single average acceleration shock signal. Furthermore; because the machine is force controlled, it is understood that the total weight and the overall dimensions of the device under test (DUT) and the fixture have significant effect on the severity of the test. Thus, measurements are repeated from the different sized fixtures and the results are compared in order to understand the effects of the fixture size and the weight on test severity.