faster than the wind

Here is a thought that will make your head spin. As you probably know a sailboat (or a sail car) can go faster than the wind speed by traveling across the wind direction. But can you go faster than the wind going straight downwind? Turns out the answer is yes, at least for this "car". If you watch the video, notice the wind flags streaming away from the direction of travel when it gets to top speed (over twice as fast as the wind is blowing). I'm still scratching my head.