The number of automobiles is rapidly increasing, as are the importance of the car as a way of transportation, and the variety of its uses. In these environments, a safety, one of the primary factors, which must be considered in automotive engineering, demands a system that aids the driver''s perception, in addition to the existing passive method, which relies on just man''s ability. In this point of view, development of the promoted system that complements the passive safety devices is demanded. A system like this should make driving safe and satisfy the need for comfort, while decreasing the driver''s burden and fatigue.The object of this paper is the development of an algorithm that warns the collision ahead and avoids this situation, using some information about the host-car, target-car, surroundings, road conditions, etc. The warning system is developed using a decision algorithm of the degree of safety. To show the validity system based on our safety algorithm. Through simulation and experimental result, the validity of our FCWA algorithm is verified.