"have seen those little holes, but I've never seen a train there. It's really cool to see trains ahead of you from the front of the train, I never understood what the purpose of the lights on them was for, though...since its all automated, so if there was a malfunction, nobody'd be able to see the other trains lights and stop the train. I've always had good luck with allignments, though."
The lights are there because it's a train
, and as such, even automated, it still has to follow FRA
(Federal Railway Administration) rules ...
Of those are that a) you have to have headlights shining bright in the direction you are travelling and b) you have to have red and green signals indicating that you are OK
to proceed, or have to stop.
The Hartsfield train system has both of those. Next time you pull in to the T-gates station, look out the nose of the train : you'll see the train ahead of you at Baggage claim. You'll see the Green signal in the tunnel turn Red, then the headlights will switch to the opposite direction, then it'll move off into the switch, to pull into the T-station on the other side.
Then your doors will close, the signal will go Green as the switch switches back to the "mainline", and you pull out and over to Baggage.
"Back on the subject of the train, out of curiosity, has anyone manged to reopen the doors once they have started to close... I have always doubted the annoucement, but never seen anyone prove it wrong..."
They do not re-open. They will grab and hold whoever gets stuck in them. If they get stuck long enough the warning message "Someone is blocking the doors" goes off, but they do NOT reopen. The person either has to get out, or squeeze in. They are usually helped by other passengers before there's too long a delay. It's not much pressure, so you wouldn't get injured, so it's pretty easy to work loose.
Note, however, the safety systems WILL prevent the train from actually moving until the door is fully closed and locked (you'll hear a locking pin "snick" into place if you're standing near the doors).