Apologies if this has been discussed, but after searching this forum and googling and looking in manual, I couldn't find much information on it. Ok, so something happened I had never seen yesterday and because I had passengers and had a lot on my mind on way to a hospital, I can't say with 100% certainty that what I'm about to describe happened exactly as written. But, it was interesting. I consider myself a diligent lane changer, always check over my shoulders after looking in my mirrors and signaling, so the following situation rarely happens to me. I was on the freeway doing ~65 mph (Autopilot off) and wanted to change lanes one over to the left on a 5 lane freeway in San Diego. I signaled, looked in the mirror, and almost simultaneously as I checked my blind spot over my shoulder (don't ask why I didn't check the instrument cluster, dumb of me), began ever so slightly to initiate the lane change (really felt confident the lane was clear). Whoops! -Someone was there, and before they had a chance to honk or maybe even notice, I was correcting back into my lane manually. However, at nearly the same time (all happened quickly) I heard a tone I had never heard before (I think a triple chime) and I swear the steering wheel was correcting me even more aggressively back into my lane. I have seen the video of the model S on AP avoid the utility truck coming into its lane, but I wasn't on AP at the time. My question is, does this sound legitimate or is any of this in my mind because I was somewhat distracted? If this is legit, can anyone point me to where this is written in the manual or release notes because I can't find it anywhere. Thanks!