Working timetable
Also: wtt, public timetable, public times
The railway’s own, more detailed timetable, as opposed to the one passengers see.
The working timetable is the version the railway runs to. It has every train, including freight and empty ones, passing times at junctions, and times to the half minute.
The public timetable shows passengers whole minutes at their stops. The two don’t always match exactly: a public arrival time can be a little later than the working one, to give the train some room.