The report of the investigation of this accident has been published by
SUST (aka SESE, SISI, and STSB). It's only in one language, in this case German which is local to Rafz. I'd expected the summary to be translated into French and Italian, but apparently not.
Since I know almost no German, and this is complicated stuff full of long words (even by German standards), that causes some problems. However, it's full of pretty pictures, so it's possible to follow the narrative parts pretty well.
For those who think the Swiss set the highest standards of "how to run a railway", the causes of the accident may be a bit of a surprise. The S-bahn train did depart against a red signal, and the emergency stop when this was realised left it foul of the points where a through track joined the platform track.
This is my take on what report identified as the main reasons:
- The drivers (trainee and trainer) mistook the green signal for the through track for the one applying to theirs. It was straight ahead, and brighter than the correct one which was to one side. I think the report even says that the design rules for signals don't include sighting confusions like this.
- The train and signalling system (ZUB) should stop a train attempting a SPAD▸ , but in this case it was not fully operative - the train had reversed at Rafz, and turning on the new driving position reinitialised the system so this autostop was temporarily inactive.
There are several other things, including a lot about the operational procedure taught for departing a station (rather than the way the learner was being supervised). That, and other points, make less sense to me.
If anyone can cope with the German, and wants to correct any errors in the above, please do.