Elon Musk writing on the Tesla blog:

Taking this one step further, a Tesla will also be able to bounce the radar signal under a vehicle in front - using the radar pulse signature and photon time of flight to distinguish the signal - and still brake even when trailing a car that is opaque to both vision and radar. The car in front might hit the UFO in dense fog, but the Tesla will not.

As you can probably guess, this is an article about the latest update to the Tesla's Autopilot system. They're doing some cool things with the radar, and I always find it interesting to see what they're up to (Even if I don't even own any car).