We've had the Y since the beginning of the year and, due to the pandemic, have not been driving much, mostly around town. Today, wife was driving and we were on an interstate highway for a few miles. Wife sees a car closing in super fast behind us, looking almost certain to rear-end our car. As she's verbalizing "oh my oh my oh my" I felt a sudden acceleration. Sudden enough and forceful enough to pin my head back against the seat. It's a measly LR, without any acceleration boost, but I tell ya, it scares me to floor it, as thrilling as that feels. Now, I was sure wife had accelerated to put some space between us and the maniac behind us, and I wanted to commend her for quick thinking and action. Turns out, she didn't do it, and she had as much of a surprise whip from the unexpected acceleration as I had. Thankfully, there was no crash, and the maniac exited the highway soon after.
But I'm wondering, did the Y sense the car behind us closing in real fast and accelerate on its own to avoid a rear-ender? The acceleration did not last long, perhaps two or three seconds--not sure if this is accurate--since there was a car in front of us. We were in such shock and awe that it occurred much later to save the dashcam video.
We have FSD, but we do not use it. At the time this happened, the Y had warned that autopilot had been disabled. Since wife never engaged it, it's a puzzlement as to why that message popped up.
So, question: is this (self-accelerating to avoid being rear-ended) a known safety feature?