Maybe it was a TGV train?

I found a 250 mph river barge on the Tunisia terrain. I think the custom terrains are going to have this problem. It looks like the trains and barges travel at whatever speed is necessary to go from source to destination in about 10 minutes.
(BTW: As any worthwhile AH pilot would do, I tried to land on the river barge going 250 MPH. I was less than sucessful.)