The factors that affect on traffic safety are human, vehicle, road and environment. In Croatia the leading cause of traffic accident is human, in just 0,2% of traffic accident the cause is some technical defect on vehicle. However, analyzing the information that on the regular annual technical inspection more than 22% of the vehicle did not meet the technical requirements, to assume is that the number of defective vehicles that causes traffic accidents is significantly higher. In order to determine the relevant statistic data of vehicle as a cause of traffic accidents, it is necessary to implement technical inspection of vehicle that are involved in traffic accident. Research objectives are to determine how many defective vehicles were involved in traffic accident, how many of them might have been the cause of a traffic accident, and which elements on the vehicle are possible cause of traffic accident.