BSD(Blind Spot Detection) has additional function which helps to keep the warning indicator from the car ahead as compared with vehicle speed, yaw rate, turn signal. BSD uses CAN communition to exchange information, which is required for control, with related ECUs and to receive input signal from the other ECU. CAN communication type is communication speed is high speed CAN and two terminal resistance is connectted in a line. BSD has a CAN controller to control signal exchange.