When you have a train which is started but standing in a station because it don't have any other station to go (I sent them to park), other trains count it as a normal train not as a stopped which can cause jams when other trains stop behind tham.
Here I have a picture about the situation one train (with solid fuel) trying to enter to my personal station, but my personal train already standing thare:
http://i.imgur.com/H0LFeDZ.jpg
And here is my personal train schedule:
http://i.imgur.com/N1PYUEm.jpg
[0.11.22] [martin] Train path finding issue
Re: [0.11.22] [martin] Train path finding issue
Thank you for the report, although I have not been able to reproduce this problem, I have added a pathfinding penalty for "taxi trains", so this should not happen anymore.