I drive one (C350e), and indeed it monitors traffic and brakes when another car in front does too. Now the question is: "does it really matter that the car can see through the car in front"? Because if the car is self-driving it will keep such a distance that it should be able to brake & stop safely if something happens in front of it. Meaning: the Tesla should still be able to come to a safe stop even if it only detected the nearest car was braking - just because of a -say 2 second- distance between the cars.