That's a much more complicated feature than you'd think.
What does the car do when someone cuts you off on the highway? You're going 60 mph and there's now an object 3 feet in front of you. The car doesn't know whether it's moving or not, it takes time to measure velocity.
Or if you're on one of those curved highway offramps with concrete barriers. There is legitimately an object directly in front of you.
Or if it's just a plastic bag that you can totally just plow into.
We can solve those problems, but it requires stuff like planning a route so you know if there are things in the path, and tracking objects around the car so you already know how fast they're going.
A naive "if object in front of car and impact will happen in less than X seconds" approach is going to misfire often, and people are going to rear-end the car when it slams its breaks at 75 mph on the highway for no apparent reason.
I have a Honda that seems to have solved all those problems. It doesn't really "take time" to measure velocity, at least in the context of moving objects with inertia and human reaction time.
There is a way to deal with emergency braking that could be considered obvious and yet ingenious, if you have radar or something that can identify solid objects.
Instinctively, you'd think these systems are complicated, and impossible to guaranteed correct behavior with.
But you might set the threshold so that braking triggers slightly after avoiding an accident is physically impossible given the required acceleration vector. That basically guarantees that you can't make things worse.
What does the car do when someone cuts you off on the highway? You're going 60 mph and there's now an object 3 feet in front of you. The car doesn't know whether it's moving or not, it takes time to measure velocity.
Or if you're on one of those curved highway offramps with concrete barriers. There is legitimately an object directly in front of you.
Or if it's just a plastic bag that you can totally just plow into.
We can solve those problems, but it requires stuff like planning a route so you know if there are things in the path, and tracking objects around the car so you already know how fast they're going.
A naive "if object in front of car and impact will happen in less than X seconds" approach is going to misfire often, and people are going to rear-end the car when it slams its breaks at 75 mph on the highway for no apparent reason.