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In road accident analysis the problem of uncertainty of calculation results becomes essential particularly when modification of input values within the adopted ranges leads to diametric change of the answer to the question posed by the court of justice (e.g. “collision from the right-hand side of the center line” – “collision from the left-hand side of the center line”, or “the accident could have been avoided” – “the accident could not be avoided”). The aim of the paper was to present a method of collision reconstruction calculation using the principle of conservation of momentum, the principle of energy conservation, and the principle of kinetic energy and work equivalence (energy balance) (Marquard), taking into consideration Monte Carlo simulation method. The applicability of the method in determination of distribution function for vehicle collision velocities was proved and, what is more important, its practical uselessness in determination of collision location.

In the paper SMASH - a computer program for road accident simulation is presented. Besides the logic of the program the models of vehicle, tire and crash itself are analyzed briefly. Data and diagrams showing the comparison between SMASH results and actual tests data are presented.

The problem of uncertainty is particularly important in the analysis of accidents involving pedestrians because even slight but simultaneous modifications of many data can result in shifting the responsibility line. Calculations include a number of irreproducible parameters whose numerical values are either selected from literature (e.g. reaction time, lag time, friction coefficient) or on the basis of verbal description (e.g.: “…when he was still running along the sidewalk, it was obvious he was going to rush into the roadway”, “the car wasn't braking too hard”). Additional difficulty is caused by performing mathematical analyses of different versions given by the witnesses (e.g.: “he was walking slowly”, “he was walking at a fast pace”), which together with other uncertain data lead to a large number of additional “subversions”. In the paper an analysis of the sensitivity of function describing the kinematics of a pedestrian accident has been made.