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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.

This article presents the results of an analysis of the yaw marks left by a car with normal pressure in all tires and then normal pressure in three tires and zero in one rear tire. The analysis is a continuation of research on influence of reduced tire pressure on car lateral dynamics in a passing maneuver, discussed in the SAE paper No. 2014-01-0466. Preliminary analysis of yaw marks has shown, that a wheel with zero pressure deposits a yaw mark whose geometry differs from the yaw mark made by a wheel with normal pressure based on which we could calculate: critical speed, slip angle and longitudinal wheel slip. The aim of the presented research was to analyze the yaw marks left by car with zero pressure in one rear wheel in order to check the possibility of determining the vehicle critical speed, slip angle and longitudinal wheel slip. It was reached by performing bench and road tests during which the vehicle motion parameters were recorded using GPS Data Logging System.