A great deal of effort has been concentrated on the longitudinal control for the collision avoidance of moving vehicles. In an emergency as well as in a normal situation, however, the steering control can be a very effective alternative as observed in the practice of manual evasive driving. In the reported methods of steering control, it is found that the dynamic motions of the neighboring vehicles are often ignored, which may result in some danger of 2nd collision. Therefore, it is necessary to assess the surrounding traffic situation to prevent 2nd collision that can occur just after escaping from the 1st collision situation. In this paper, we tackle the collision avoidance problem when steering actuation control is allowed in consideration of the dynamic motion of the neighboring vehicles. Specifically, a hierarchical control scheme is suggested as a feasible solution, and the proposed system is verified via simulation using a software simulator called DevACAS (DEVeolper of Active Collision Avoidance System), which we have developed.