Originally Posted by needmoregarage
I agree DTMiller - and I think my explanation was inarticulate. If someone cuts in front of someone with the braking system - the car that was cut in front of will brake hard when it senses a car suddenly in front. If anyone is following them and not expecting it (even if they are at a reasonable distance) - toward the end of a straight where speeds are high and lots of ground is covered every second - if the driver in the following car does not expect hard braking ahead, and doesn't react immediately, or has someone on their tail....it could be serious. It could easily become a chain reaction if enough cars are following in close proximity.
Still not sure I'm drawing a "clear" picture (even though I can imagine it in my head I don't know if I'm articulating)
That is unlikely to happen because the brake application is triggered by the relative speed of cars more than the distance. So if the car cutting in front has the same or higher speed, the system will likely not trigger, maybe just do a warning beep. I'm describing this based on my experience with the current gen Cayenne.
Where this system can be dangerous is when a car with such a system is passing and gains passing speed while still behind the car being passed, even if partially (e.g., to use draft or to have a better line). The system does not "know" that the driver is about to turn and pass the obstacle and assumes the obstacle is getting rear-ended. Happened to me once.
Unlike other nannies, this one can actually be very disruptive and dangerous even for a relative beginner. And it only helps if you are not paying attention, which should not happen on a track anyway. So I'd turn it off as a matter of policy.