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. A specific parameter involving the total initial momentum, collision energy loss and velocity change, ΔV, of a single vehicle remains remarkably constant throughout all experimental collision types, speeds and vehicle mixes. This allows a simple expression to be used to predict approximately the ΔV of either vehicle in any collision.