Agreed, that's one way. The other way is multiple downward facing cameras with stereoscopic vision of the area immediately around the car. Mobileye demonstrated

Agreed, that's one way. The other way is multiple downward facing cameras with stereoscopic vision of the area immediately around the car. Mobileye demonstrated a system like that and it worked really well. Tesla's cameras have huge blind spots near the car and aren't stereoscopic in all directions. They had ultrasonic sensors at one time, but those had blind spots and major limitations too.