Locations on the rail network can be identified by several different methods:
- 3-Alpha Codes - A 3-character code used for stations. Previously referred to as CRS (Computer Reservation System) or NRS (National Reservation System) codes.
- NLC (National Location Code) - A 6-digit code. These includes physical locations such as stations and junctions as well as codes relating to accounting and other purposes.
- TIPLOC (Timing Point Location) - Codes relating to points used in deriving train schedules
- STANOX (Station Number) - These codes can refer to non-station locations such as sidings and junctions. STANOX codes are grouped by geographical area - the first two digits specify the area in which the location exists. See the STANOX code areas page for details.
- ATCO Code - Used by multi-modal journey planners and timetables
A single location may have multiple codes representing it, and different sets of platforms in one location may have differing codes - see the multiple codes section below.
See the reference data page for sources of these codes.
|Glasgow Central High Level||GLC||981300||GLGC||07257||9100GLGC|
Emil Vaughan asked, "There appear to be two CRS codes used for Highbury and Islington in the ATOC timetables: HHY and HII. The first is used for the Overground, and the second for the deep-level FGW services. Only one of the codes, HII, is in the NaPTAN RailReferences.csv file. I was wondering how common it is for a station to have multiple CRS codes? Thanks!"
It is reasonably common for a station to have multiple TIPLOC codes, where it consists of multiple groups of platforms on completely different lines. London Bridge, Victoria, Clapham Junction, Reading, Liverpool South Parkway are all examples of this I can think of off the top of my head. These different TIPLOC codes are used in schedules.
A lot of the time these different TIPLOCs will additionally have a CRS code assigned to them (as in the case of HII for the Highbury & Islington low level platforms), but as far as I can see these secondary CRS codes are never used for anything, at least not in any of the public ATOC and Network Rail data. Yes, they appear in various indexes and master lists, but not elsewhere.
HHY is definitely the main CRS code for Highbury & Islington; you can check this in the ATOC master station names file (TTISxxx.MSN) downloadable from data.atoc.org.
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