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Technical Paper

Energy and Major Diversion in Accident Reconstruction

Special methods of momentum-based accident reconstruction often are required when path diversions are major, that is, in excess of about 45°. An energy-based component is well known to be required for the maximal path diversion of 180″; with parallel unknowns the two momentum equations become identical, so that an independent equation based on the observed damage is required. Also-as we demonstrated in a previous paper-in intersection impacts, even with modest path diversions, momentum loss to earth during impact, while classically neglected, appreciably affects the inferred momentum of approach. The present study shows further that, with major diversion and brief travel to rest, conventional neglect of travel during impact may greatly distort the assigned post-impact travel direction and/or distance and, in consequence, the momentum solution.
Technical Paper

The Effects of Measurement Uncertainty on the Reconstruction of Various Vehicular Collisions

This paper continues a previous study of the effects of uncertainty of measurement upon accident reconstruction. The task is to identify, given the many inevitable errors of observation, the few of greatest import, so that these errors may be reduced, and to document the accuracy of the associated reconstruction. Until recently, it was not for lack of method that such studies could not be properly performed, but for lack of good data on uncertainty of measurement. The essential data was provided in 2002 in a report by Bartlett and others of juried studies performed by volunteer field investigators, summarized and supplemented in 2003 by Bartlett and Fonda in the form of a single table of all likely errors of measurement (furnished again here). In that paper, Finite Difference Analysis (FDA) was reviewed and with the aid of the new data was applied to automotive accident reconstruction.