Close Encounter of a Deer kind

I would almost think a deer would need to stop in front of you for the car to trigger. They usually fly across in front of you so they are hardly there long enough to trigger an event. I had a deer spring in front of me at the very last second and clip the front of my car with a hoof, it didn't leave a mark or anything but certain got the blood flowing. This was in a different car but I doubt that any technology would have had a chance to detect and do anything about it. I am still not sure how the deer got through 8 lanes of traffic but only clipped me going up the offramp. Talk about threading the needle.

 

I have to admit, I don't know very much about the alphabet-soup of Toyota's Safety Systems, but they appear to rely on a forward-looking radar (ACC Radar.)
Something like this:

The area in blue represents the radar coverage, the pink is for the camera(s) that I don't think that Priuses have.
They used to use Lidar (Laser) and I've heard of people tinkering with ultrasonic sonar as well.

Here's the deal with ACC:
It's forward looking, and white-tailed deer aren't armor plated.
If they were, then they would be more radar reflective.
If they just stood in the road.....transfixed by the pretty white lights bearing down on them then it would give the Prius more time to plot the object and compute a CPA, and determine whether or not preventative braking is warranted.
Deer represent a special challenge for collision avoidance because they're not radar (or laser) reflective AND they don't like to move in predictable ways......pretty much because they don't want to be eaten and they regard any large, fast object and a predator trying to eat them.

So yeah.....things like deer, kids chasing balls in neighborhoods, and all manner of other things are still going to represent a hazard for cars probably for as long as there are deer, kids, and cars.

The REAL tough choices lie ahead!!!!
Someday cars are going to be (allowed to? required to?) make tougher calls like:

"Hmmmmm.....should I hit the School bus full of kids, or drive me and my owner off the cliff?"

....Stay tuned.

Laws of robotics - Wikipedia