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The National Highway Traffic Safety Administration has conducted twelve staged collisions with the purpose of furnishing collision data for use with accident models. In this paper the data is fit to a two-vehicle impact model using the method of least squares. The model is based upon the equations of impulse and momentum; the computed constants are the coefficients of restitution and equivalent coefficient of friction. A gradient search technique was used to minimize the suns of squares directly. Solutions (coefficients and velocity components) are found for 11 NHTSA collisions. The data seems to fit the model well, although deviations of 10% in impact velocity changes are not uncommon. Collisions with similar geometry but different initial velocity magnitudes do not always result in similar values of coefficients of restitution and friction.

The force distributed over the contact patch between a tire and a road surface is typically modeled in component form for dynamic simulations. The two components in the plane of the contact patch are the braking, or traction force, and the steering, or side or cornering force. A third force distributed over the contacts patch is the normal force, perpendicular to the road surface. The two tangential components in the plane of the road are usually modeled separately since they depend primarily on independent parameters, wheel slip and sideslip. Mathematical expressions found in the literature for each component include exponential functions, piecewise linear functions and the Bakker-Nyborg-Pacejka equations, among others. Because braking and steering frequently occur simultaneously and their resultant tangential force is limited by friction, the two components must be properly combined for a full range of the wheel slip and sideslip parameters.

Little experimental data have been reported in the crash reconstruction literature regarding high-speed sideswipe collisions. The Insurance Institute for Highway Safety (IIHS) conducted a series of high-speed, small overlap, vehicle-to-barrier and vehicle-to-vehicle crash tests for which the majority resulted in sideswipe collisions. A sideswipe collision is defined in this paper as a crash with non-zero, final relative tangential velocity over the vehicle-to-barrier or vehicle-to-vehicle contact surface; that is, sliding continues throughout the contact duration. Using analysis of video from 50 IIHS small overlap crash tests, each test was modeled using planar impact mechanics to determine which were classified as sideswipes and which were not. The test data were further evaluated to understand the nature of high-speed, small overlap, sideswipe collisions and establish appropriate parameter ranges that can aid in the process of accident reconstruction.