I couldn’t get them to work reliably at all in an automated manner. I think I beat the level that needed them by mostly manually operating them, and then got fed up.
> Since 2.0 it's quite straightforward using interrupts
Yes. It would occasionally work once or twice, then stop. Just wasn't reliable. I have no idea what I was doing wrong, but:
1) I've installed -> played -> struggled with trains -> gave up and uninstalled the game about four times now.
2) The last time I tried every setup and combination I could think of, and also every tutorial, forum post, and Youtube video I could find, to no avail.
Not sure what version you played, but since 1.0 the game is very explicit about why train is not moving (no fuel, no path, destination full, depart condition is false).