When software 8.0 was released by Tesla, one of the features that Elon Musk promised would be available was the ability to see a few cars ahead through enhanced radar.
That ability is tested here by Bjorn Nyland in this video showing that the Model X detects braking from two cars ahead and begins to react on its own.
"With software version 8.0, the radar can now see two cars in front. When the frontmost car brakes, the car in the display will turn white. I did several tests and measured the time from when the brake lights on the middle car turned on to when my car slowed down to be 0.2-0.4 seconds."