The goal of article is to point out issues connected with calculation uncertainties within traffic accident analyses and to devise a suitable methodology with which it could be possible to describe particularity of the problem. The care was dedicated to the calculation of following variables: vehicle speed at the beginning of traffic accident, distance travelled from the starting point of driver´s reaction to the collision point, distance within which a vehicle has stopped in front of, or beyond the collision point in case of proper driving technique of driver. When solving complex analysis of traffic accident then in few cases it can happen that technically acceptable interval of input values leads to ambiguous conclusions – if the driver could avoid the traffic accident with proper driving technique. Solving of this question is crucial also for right assessment of traffic accident cause. This article therefore deals with these cases.