[richard in NC]

I studied up on collision warning on the 5. I don't know if it works the same on the M2 and I've not explored it specifically. On the 5 you can adjust the sensitivity to early/normal/late. I've kept mine on normal. It also has 3 levels of detection/intervention depending on distance and closing speeds..

Over 2 years of city traffic, I've had all 3, in order of severity: 2 beeps and red warning symbol, several fast beeps and flashing symbols, and actual braking. It seems to brake as hard as needed, near threshold levels if need be. If paying attention, the car seems to react a split second faster than you. IE my foot is heading to the brake as I get the alerts and/or it braking.
Once on track, I was catching a Miata going 40-50 mph faster than it going into a braking zone. I got the warning and then braking just as I was about to nail the binders behind it. I've also had it nail the brakes when pulling out of a shoping center and a cyclist goes whizzing by the front of the car, from the opposite direction I was looking. That was odd, look left, give it gas to pull out when all clear, move 2 feet and, wham, its on the brakes, stops the car, and beeps as the guy flies by from the right. I missed him by a foot.

Note I can disable the braking but still get warning beeps and an iDrive alert that I should re-enable it.

On the M550i I also have pedestrian/animal detection, and night vision that even does that in the dark. I've gotten several warnings over the 2 years. It's especially cool with all the deer in WV at night.