SPY blind spot detection is a very useful device to keep the vehicle safe when changing lanes on the freeway or in the evening, especially driving in rainy / snowy / foggy weather. The system will analyze the reflected signal sent by two microwave radar sensors behind the car. When there is another vehicle approaching the blind spot, the LED indicator will be on. At that moment if the driver turns on signal lamps to attempt changing lanes, the system will emit Di Di Di sound and LED indicator flashes quickly to warn the driver not to change lanes.