While four-character train descriptions are the primary method of identifying trains, they are not necessarily unique to that individual train. Headcodes are often repeated on a cycle throughout the day (for example, services on a certain route be assigned 2C20, 2C22, 2C24, 2C26 and 2C28, then jump back to to 2C20); and in the earlier years of the system all services with the same origin, destination and service pattern (or even same general route) would use the same TD throughout the day.
This creates issues in SimSig when specifying activities, as there's an obvious requirement to reference a specific schedule. Hence, UIDs are used to distinguish schedules with identical TDs. The UID is only displayed in the timetable editor and F2 train list. When referencing a UID, a $ sign is used followed by the UID. For example, when creating a next working activity for a train which is to follow the schedule 2D40 with UID 12345, then "$12345" should be entered in the next working box. This will be displayed in the 'show timetable' and other windows as 2D40, with SimSig using the UID internally to distinguish the specific 2D40 schedule to use.
In timetables set since the introduction of electronic timetables on the rail network, the UID is usually the schedule ID used in Network Rail's timetabling system (and can be found on sites such as Real Time Trains).
A UID does not have to be specified for all, or indeed any schedules, however where schedules share a TD it is strongly recommended to add a UID.
UIDs may contain letters, numbers and hyphens only.
Last edited by Steamer on 08/01/2024 at 18:35