To simplify, radars can see how far away objects are and how fast they're moving but only dimly in what direction they are. So if you don't want your car to br

To simplify, radars can see how far away objects are and how fast they're moving but only dimly in what direction they are. So if you don't want your car to brake every time you pass under an overhead sign or over a metal grate you need to filter out non-moving returns to some extent. At a certain distance the cone of the radar should only be intersecting things that are actually a danger and you can start braking. But it's really good at noticing if a moving object has changed speed, like the car in front of the car in front of you braking. On Teslas theoretically the camera is there to prevent stuff like this but vision AI isn't all there yet. Other companies use lidar which gives pretty accurate distance and direction but not object speed. Pretty useful for avoiding obstacles but current automotive grade lidars are very expensive. Much cheaper solid state lidars seem to be imminent.