An imaging system for a vehicle is provided for distinguishing between tail lights of another vehicle and a flashing red stop light. The system includes an imager configured to image a forward external scene and to generate image data corresponding to the acquired images; and a processor configured to receive and analyze the image data to identify red light sources and to further analyze each red light source to determine if the red light source is detected for a predetermined time period. If the red light source is not detected within a predetermined time period after it is detected, the processor determines that the red light source is a flashing red stop light. Otherwise, if the red light source is detected for a predetermined time period, the processor determines that the red light source may be a tail light of another vehicle.