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The trajectory solution procedures of the original CRASH program included both the SPIN routine and an exploratory trajectory simulation option to approximate and refine the linear and angular velocities at separation. The resulting separation speeds were then used to determine the impact speeds by means of application of the principle of conservation of linear momentum. This paper presents a detailed review of the logic, rationale and limitations of the trajectory solution procedures of the original CRASH program and discusses a number of refinements including: incorporation of the principle of conservation of angular momentum, approximations of the effects of changes during collision in the positions and orientations of the two vehicles and of the effects of external forces and moments that act on the two-body system during the collision, and adaptations of optimization techniques for error reduction and convergence in iterative solutions.

Effects of restitution on damage interpretations are compounded by the fact that restitution acts to reduce the amount of residual deformation, for a given maximum dynamic crush, while also acting to increase the total impact speed change. This paper presents a revised analytical procedure to include restitution effects for the CRASH program and refinements to the restitution modeling within the SMAC program. The conversion of vehicle impact test results into inputs for the two revised programs is also included. The effects of the refinements to the damage analysis procedures on reconstruction results are illustrated by direct comparisons with corresponding results produced by the original SMAC and CRASH programs and with measured data from full scale vehicle impact tests.

Research performed in the 1970's revealed significant limitations in the available documentation of vehicle crush information and trajectory spinout information. As a result a series of full-scale crash tests were performed which became known as the Research Input for Computer Simulation of Automobile Collisions (RICSAC) crash tests. Previous research using the RICSAC test results, particularly in relation to the validation of accident reconstruction computer programs, has varied widely in acceptance, interpretation and presentation of the RICSAC test results. This paper presents a detailed review and decipherment in useable form of the original 12 crash tests that were performed within the RICSAC program. A new method of analyzing accelerometer data from arbitrary sensor positions, on the basis of discrete measures of the vehicle responses rather than complete time-histories, is defined.