BSD Radar Blind Spot Detection System for Reminding Driver when Changing Lanes on the Road. The system is activated automatically when vehicle speed is more than 20Km/h, the LED indicator turns on if sensor detects another vehicle in the next lane coming closer. If you switch on your turn signal at the same side when object is detected, the LED indicator will flash, and you will also hear the beeper. If you switch on hazard/emergency signals the LED indicator will not flash. When vehicle speed is lower than 20Km/h.