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The Simulation Model of Automobile Collisions (SMAC) computer program was developed by Calspan Corporation as an aid with which to accurately reconstruct road accidents. Part of the overall objective of the research has been to make the system “user oriented” so that users without an engineering background can operate it with ease. This has necessitated developing a START program which automatically runs the SMAC program from a minimum of input data and an iteration routine designed to optimize the input values of velocities to provide a “best fit” reconstruction to the available scene data. A summary of how the START program works is given; however, emphasis is placed in the paper on the development of the iterative routine. The theory behind the routine is given and a number of examples are then presented to show how it works. For each example the results of each successive iteration are given to illustrate the manner in which the program converges to an acceptable reconstruction.

This paper reports the application of the Simulation Model of Automobile Collisions (SMAC) computer program to selected cases of actual highway accidents. Since SMAC was developed to allow accidents to be accurately reconstructed by operators without a detailed knowledge of engineering mechanics, recent developments have concentrated on providing a Start routine. This program automatically generates the inputs required for SMAC, including collision speed estimates, from a minimum amount of information available at the accident scene. A brief summary of how Start works is given, followed by a discussion of actual cases. The sensitivity of the final reconstruction to the various program inputs is discussed; this gives an indication of how the initial Start inputs may be adjusted to obtain a best fit with the minimum number of iterations of the program.