The first maxim of safe railroad operation is that two trains not be allowed to occupy the same section of track at the same time.  There are all sorts of ways to ensure this, the simplest of which involves the use of a timetable, and the only necessary technology is synchronized watches.  Let us review the purpose of the timetable.  "Note, in railroading, that a timetable does not REQUIRE a train to be at a station at the specified time. Rather, it means that the train will not be BEYOND that station BEFORE that time."

In the course of reporting on the Bad Aibling interurban collision, I became involved in an instructive (now closed) discussion on this article, in the course of which a participant cited the normal timetable. The wreck occurred during the morning rush hour.
The 6:37 train from Rosenheim to Holzkirchen arrives Kolbermoor 6:40 and should depart 6:45 AFTER the 6:10 Holzkirchen to Rosenheim train arrives Kolbermoor 6:44.

The Rosenheim bound train was delayed but unfortunately the Holzkirchen bound train did not wait and departed on time.
Here's where the failure of the signalling system, whether by accident, or by deliberate error, arises.

Under normal procedure, the Holzkirchen train will not be BEYOND Kolbermoor before 6:45.

Under North American timetable and train order operation, the dispatcher can hold the Rosenheim train at Bad Aibling for the Holzkirchen train.  With centralized traffic control, it's even easier.  Provided the Rosenheim train has not yet accepted the signal at Bad Aibling, he simply takes away the Bad Aibling to Kolbermoor section, and clears the route from Kolbermoor into an open track at Bad Aibling.  The circuitry prevents conflicting routes to be set.

And yet, two trains occupied conflicting routes. Investigators are now alleging human error.
An investigation has now been opened into the actions of the controller who was in charge of the stretch of track in Bad Aibling south-east of Munich on the day of the fatal crash.

If the controller “had acted according to the rules and according to his duty, the collision would not have happened,” lead prosecutor Wolfgang Giese said in press conference held on Tuesday afternoon.

"There is no evidence of technical problems... Our investigation shows that this was human error with catastrophic consequences," he added.
Authority to run Rosenheim to Bad Aibling laps authority to run Bad Aibling to Rosenheim.  Broken trains and dead people.  It's a lesson as old as railroading.  The Crusty Chief Dispatcher continues to teach it.


David Foster said...

Shouldn't the interlocking prevent the controller from clearing signals that set up a conflict?

Stephen Karlson said...

Yes, unless (as appears to be the case here) the dispatcher overrides it. The report from the German version of the National Transportation Safety Board will be instructive.

I'm particularly perplexed by the motorman of the train headed for Bad Aibling not waiting for the train coming from Bad Aibling. Supposedly that train was running about four minutes late; the running time from siding to siding is six minutes. You don't deviate from the running timetable without a lot of special permissions (don't get me started on not restricting the rights of a train at the station where its rights are to be restricted.)