The way it has been done is that the car is coupled to the end of the regular train. The whole event took about an hour and a half, I seem to recall that it was about four round trips before we had to leave so they could prepare the car for the next seating. You get some interesting looks from the people in the station que, as well as at the crossings. After our dinner when we were out in the park (we bought regular park tickets that day) I was approached by a couple of people inquiring what was going on.