TL;DR
Train alerts for "no path" conditions, missing stations, or whatever else causes train dysfunctions in automatic mode.What ?
If it has no path, or if the station doesn't exist, or something else causes the trains not to function in automatic mode, and effectively block traffic or not operate, display an alert.The alert could be placed in the same place where other alerts pop up.
Having the alert also show up on the map would be ideal, similarly to how construction, logistic, and damage alerts show up.