1.through installing 2pcs of 24GHZ  microwave sensors into car rear bumper, when the car in moving,if any moving object closer to blind area( 3 meter from right and left side ,15 meters from behind）,the object will be detected by system sensor , the LED indicator will turn on and keep shining for reminding driver,in this condition,if the driver wants to change the lane or reversing ,the buzzer will beep sounds and LED shinning for reminder                                                                 

 2. with GPS speed control ,without false alarm