Did you guys ever read the story "The Great Train Robbery"? It was a true story about the million dollar heist in Great Britain around 1960. Fascinating book, although, sooner or later all of the robbers were caught. But the significant part, alluding to this topic, is that they were able to stop a train by changing the apparent aspect of a signal, without notifying the dispatch office of what they did. Very clever, and it did work for their needs. They stuffed a work glove into one aspect to hide the green light and used a lantern battery to light the red aspect.
Incidentally, Rover, Land Rover vehicles had been used in the heist, and some time after the robbery, Rover published a really cute advertisement about how, if you were planning a train robbery, Rover vehicles were the best suited that were available!
Great book, if you can locate a copy these days.
Paul Fischer