Investigation or estimation of vehicle collision speed is one of the most important tasks during traffic accident analysis. The speedometer needle is sometimes stuck showing possible speed data especially at severe road accident. That is generally an additional possible indicator for speed estimation for forensic expert. The paper is aimed at accuracy and differences between real speed data and display of speedometer needle data. The possible data inaccuracy can be observed during vehicle braking or in cases of driving stability loss (vehicle skid). Results of correlations between speed registered by speedometer and actual speed have been found during lock-up of wheels through stability loss skid, during acceleration with spinning wheels, and during braking manoeuvre measurements at various friction conditions. Through aforementioned manoeuvres, significant data differences have been shown and explained in this paper.

speedometer, velocity, vehicle, comparison, difference