It is the operator that is liable for personal injuries in traffic accidents. This operator concept, which is the party liable for damages not specified under the Civil Act, elicited many arguments. In connection with the operation concept, there were conflicts over various theories, such as motor theory, traveling equipment theory, essential equipment theory, garage access theory, and danger theory. As such, judicial precedents and mainstream scientific theories follow the essential equipment theory or the garage access theory. With the revision of the Act on Compensation for Car Damages (1999) and the Commercial Act(1991), the concept of operation is increasingly being defined more broadly,and this aims to better protect victims under related laws. When it can be evaluated socially that the concept of operation was used in relation to the essence or risk of transportation means, the danger theory on operation is deemed to be justifiable. Classical theories alone cannot sufficiently explain the meaning of operation associated with the recent complicated traffic accidents. In connection with the operator, there are external standard theory, dualism and monism conflicting one another, and there was initially external standard theory, but the dualism prevails in the theories and judicial precedents concerning car accidents. In other words,the concept of operation dominance was derived from the principle of liability for risk, and the concept of the benefit of operation was derived from the principle of liability for compensation; thus, the person, who is the dominator of operation and that is the beneficiary of operation, is regarded as the operator, allowing him to be acknowledged as the responsible party. However, in recent years, monism is emerging that the operator, so long as he is the dominator of operation, is liable for operation. In consideration of the Act on Compensation for Car Damages purporting to protect victims, the benefit of operation is a very subjective, abstract value of the operator, and a symbol of operation dominance, but does not determine the nature of the operator. Thus, monism holds valid. In connection with verification responsibility for the nature of operator, there are specific theory, abstract theory, and indirect contrary evidence theory; thus, judicial precedents hold the position of abstract theory that unless special reason is proved that the person, as the party reliable for damages, lost the dominance of operation, he is endorsed as the operator. The position of the mainstream abstract theory and judicial precedents is justifiable, and this is because it is not easy for the victim to prove the operator nature of the assailant given the accidental and momentary nature of traffic accidents. Thus, it would suffice for the victim to prove that the assailant is the possesor in traffic accidents, and for the assailant to be indemnified against liability, it would be valid that he should specifically prove that he lost the status as the operator.