Millimeter-wave radar works on millimeter-wave range.  It detects object distance, direction and dimension by analyzing its remitted radio frequency reflection.  The typical usage of this type of radar includes collision warning system on vehicles, defense monitoring system and tracking system on aircrafts etc.  The most current ones are capable of recognizing and differing pedestrian and vehicles.
 
24Ghz radar system used on vehicles utilizes single-wave transmitting, and single-wave, dual-wave or multiple-wave receiving, increasing accuracy and detection range.  It has potential not only in automobile industry, but could also be useful in IoT, lightning industry, drones and robot industry.
HD united(或其他车悦英文名)BSMS/LCAS uses 24Ghz high performance microwave radar that operates reliably in all conditions, and eliminates most blind spots by its wide detection range.  The technology has been continuously refined. 
The mirror warning lights would bring up attention, without disturbing the driver
The B-pillar warning lights would provide rear passengers outside hazard warning before opening doors.