Abstract
To improve the performance of Automatic Collision Avoidance Systems, it is essential to consider the vehicle dynamics when the vehicle with the system urgently avoids an obstacle in downhill. In this paper, we confirm the performance of Automatic Collision Avoidance System on the decline road by computer simulation. In case of the steep downgrade or quick steering wheel speed, it is shown that the vehicle motion is not straight after end of automatic steering input. Finally the cause of such vehicle motion can be considered by yaw-rate time series data.