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A number of simplistic formulae, based on particle dynamics, energy, and momentum methods are routinely employed by accident reconstructionists to calculate vehicle speeds immediately prior to impact. It is almost always the case that scene evidence and other information regarding important variables involved in such equations must either be estimated or can be measured only in an approximate way. In the present work, we examine the sensitivity of such standard calculations to variations in the measured or estimated values of the independent variables needed for calculation. The traditional methods of the calculus are employed. Example problems illustrate the difficulties faced by accident reconstructionists as they grapple with incomplete and/or estimated values for important variables, and with the inherent sensitivity of some of the calculations to seemingly small variations in variable magnitudes.

The very high speeds achieved by IndyCars at the 1992 Indianapolis 500-Mile Race and practice have led to a complete reconsideration of the safety implications involved in the sport. The present work describes calculations performed in order to totally redesign and reconstruct the outer concrete retaining wall and fence structure at Indianapolis Motor Speedway (IMS), to ensure spectator safety. Car capabilities were first examined to ascertain energies involved in realisticcollisions with the wall at racing speeds. A series of practice and race accidents was examined via frame-by-frame video analysis, and further calculations performed to refine energy calculations. Calculations and actual accident analyses indicate that a substantial amount of kinetic energy is lost before car-to-wall impact can occur through aerodynamic drag and tire scrub. Wall strength requirements and estimates of impact forrealistic car speeds, spectator visibility and construction were also computed.