When I modified a railway junction so that the straight track used a bridge over the junction, while turning vehicles took a side route, the next few trains using that track did not use the junction properly. The first one tried to go straight on through the bridge (not over), and somehow ended up on the track underneath the bridge. The next one, which wanted to turn right, just straight through the bridge as if the track configuration had not been changed.
Alex,
thank you for your report. Is this specific to Experimental, I wonder? Routing of vehicles has not been changed greatly. If it is specific to Experimental, it would help to have a saved game in which the problem can reliably be reproduced in order to try to fix it.
I had a similar issue in the server game when I diverted my track up onto elevated south of Elfield. The trains that had already left their stations tried to follow the old route and ended up on a dead end track. I guess if they predetermined their route upon departure, and didn't recalculate their route until they could go no further, but in this case that was too late to be able to choose a valid route and they were unable to reverse their way back to a valid route due to one way signaling.
I really do suspect that this is an issue equally present in Standard - can anyone test?
This behaviour is also in Standard. Once a train has calculated its route, if you change something in said route, you'll end up with funny results.
"Funny results": more precisely, the train will carry on following its pre-booked route until it meets an obstacle (be it a wrong-way signal or a junction or...) -- which can lead to chaos.
The way to get around this is to force vehicles near the track alteration to recalculate their route (by opening and closing their 'schedule' windows).
I'm reposting this in the standard bug report forum. Opening the schedule is the work around I've found, but can be a nuisance for long distance lines, and also if a train happens to be about to climb a slope, as it can't accelerate past about 7km/h once on the slope.