The rest of the body panels "could be made" but in this example we're only talking about the tail gate. Have you come to terms as to why this isn't perpetual motion or how is it possible for a vehicle to create it's necessary energy on the fly?

Only the arrow from behind exists. The arrow from in front of the line of travel is negated by a distorion field inside the tailgate - which masks the ability of a pressure wave knowing that it needs to exert from that side of the panel. 

 

skip to 2:15 on the video... if you could make this a one sided reaction - the barrel would move down the road.

https://www.youtube.com/watch?v=JsoE4F2Pb20