STP and overlays
Also: short term planning, overlay, permanent
How the timetable says “this train is different on these days” without rewriting the whole thing.
Example
The letters
- P
- Permanent
- O
- Overlay
- C
- Cancelled on these days
- N
- New, short-term only
The long-term timetable is made of permanent schedules. Then the short-term plan (STP) changes them for particular dates, for engineering work, events or holidays.
Every schedule carries a letter. P is permanent. O is an overlay, which replaces a permanent schedule on some dates. C cancels it on some dates. N is a new train that only exists in the short-term plan.
To find what a train actually does on a day, you take its permanent schedule and let any overlay or cancellation for that day win.
In Trainiac
Trainiac applies these whenever it looks up a train.