Yes, but that doesn't change things.. Radar is line of sight too. If it doesn't slow down when cresting a hill, you run the risk of a collision with an object beyond the crest... Radar is also lower resolution/granularity... When going down a road, Radar cannot reliably give you relative position of nearby objects in relation to visual cues. If there is a stationary object and you are in motion, radar will have a hard time knowing if that object is in the roadway in between lane markers, or if it's above the roadway, or off to the side of the markers, etc... This is why most radar systems will only track objects that have relative motion of 3mph or more. This is also why many radar systems can track a vehicle slowing in front of you pretty well, but struggle if you approach a stopped vehicle, like a parked vehicle in the roadway, or you come upon traffic where traffic is already stopped and isn't moving.But radar cars don't slow down in the same situation.
Note: One of my previous jobs was doing research in 3D positioning, using vision, laser, ultrasonics, and RF.