Thank you for your response - that is helpful. I do not think that a procedural system is really suitable for full timetable based automation of a large layout, as I need to be able to amend the timetable without having to reprogram (and debug) a script - for anything non-trivial, it is important that data be separated from code.
Is there no means of achieving timetabling in JMRI with a higher level of abstraction?
James E. Petts