I was driving northbound on I-280 in Northern California towards San Francisco with Autopilot fully engaged (speed and steering) in my wife's X. I had my hands on the wheel, was paying attention, and had my wife with me in the passenger seat. We were in the left-most lane, going ~70mph with the flow of traffic. All of a sudden, the early collision warning started beeping at me and had correctly deduced, faster than I had, that the cars ahead of me were braking hard. For a split second, I wondered if I should let the Autopilot solve the problem, but it didn't feel like it was braking hard at all, and I just wasn't ready to trust it for something like this. As I took over and stomped on the brakes as hard as I could, my first thought was how surprised I was that there was a noticeable increase in the braking effort as soon as I took over. As we were slowing down rapidly, I watched the two cars in front of me collide. For a split second it looked like we might brake in time, but alas, we did collide with the rear of the 2nd car. It was pretty light, I didn't even see any paint transfer between the two cars, my guess would be maybe 5mph? No one was injured, but I have to admit, I was very surprised and it's shaken both my wife and I's faith in Autopilot and the Automatic Emergency Braking System (AEBS). The early warning system did catch the accident occurring faster than I did, so in the end, the Tesla certainly helped mitigate the damage and keep everyone safer, for which I'm grateful. But at the same time, this seems like exactly the type of collision they're designed to avoid, and one of the major reasons we bought new Teslas in the first place. After the accident, I checked my wife's settings, and saw that she was using more aggressive settings (2 on following distance, Medium on collision warning) on her car than I use on mine (5 on following distance, Early on collision warning), but I would still think those settings must be designed to work, or else they wouldn't have them configurable like that to begin with? I've emailed Tesla about seeing if they can analyze the data and give us any feedback or at the very least feed it into their machine learning, but that was nearly two weeks ago and I still haven't heard back. Has anyone else had any similar experiences? Has anyone managed to get Tesla to look into a report like this? If so, how?