My 2015 Model S does that too. And also often detects stationary vehicles that it thinks might be in the way.

The Subaru wouldn't stop for a stationary vehicle though. Most of those systems either don't work at all for stationary vehicles, or work far less reliably. They're mostly designed for the case you described - car ahead slows suddenly and the driver isn't paying attention.

Care to clarify what you mean here? Had a subaru outback with eyesight a few years ago and I tested it with stationary objects in path multiple times (cardboard boxes and such). The subaru braked and stopped short of the objects 100% of the time.

When the vehicle you're about to collide with is moving slowly, there are good radar returns, so you can use both vision and radar to make the decison.

When the vehicle is stationary, the radar data has to be heavily filtered because radar has poor angular resolution and there are a lot of other stationary objects, many that you don't want to stop for at similar angles, like overhead road signs. That means you're relying purely on vision, which alone has a lot of false positives and negatives, so detection thresholds need to be set much lower.

Doesn't mean it won't work. Just means it's less likely to work, especially in the dark and the rain, where radar would normally be a big part of the signal.

When I was driving a 2014 Volvo, it also automatically stopped before hitting a stationary cardboard box (up to 30 kph)

Not all these systems are radar. Subaru uses cameras, in fact.

> Most of those systems either don't work at all for stationary vehicle

Citation needed. Subaru claims their eye sight system will detect and attempt to brake for a stationary vehicle. Whether or not they’ll managed to halt the vehicle is obviously speed dependent, but obviously slowing down before the crash is vastly superior to maintaining speed.