The Use Case for "where's my train?"
As Paul Clarke has pointed out on his blog, not once, but twice, "I assert that train operators know where their assets are: it would be irresponsible if they didn't. And that this information is held within their internal systems".
Here's a good use case for his proposed solution ... wheresmytrain ...
Piccadilly Circus Tube station, Bakerloo Line southbound platform, round about 5.00 PM. The dot matrix displays tell us ... that a train is "held" somewhere but with no information as to what this means. The platform announcer tells us "the Bakerloo Line is currently suspended" and immediately afterwards the "control room" tells us that "a good service is currently running on all London Underground lines".
One is these statements should be correct, the other two should not be. By means of resolution, an Elephant and Castle train turned up 2 minutes after all of this has occurred, making all three of the above statements erroneous.