Signal box prefix codes

Croydon Tramlink signals

Croydon Tramlink signal codes can be found on the Croydon Tramlink Unofficial Site.

Docklands Light Railway signals

Although the Docklands Light Railway is an automated system, trains are driven manually in the depots. At present, only five signal codes are known, all for Poplar depot. These are AS, AT, DA, DB and WA.

Edinburgh Tramway signals

It appears that the only labelled signals are in the depot area or are points indicators with codes based on the nearby station. In addition, road traffic crossings are labelled sequentially from ET1. Prefixes known at present are:

Code	Area

'Stop' signals are labelled in the form DEP R1 04 (in three rows), points indicators in the form HAY PPI 02 (again in three rows).

Glasgow Subway signals

Most signals appear not to carry a prefix. Those seen with a prefix carry A.

London Underground signals

London Underground (and its predecessors) has a complex signal labelling system. A summary can be found below. Note that the Underground is not my particular speciality: most of the raw data coming from District Dave's site (Page 1, Page 2, Page 3 broken links), and from Tube Prune (these sources are not identical), in addition to other observations. In addition to these codes, a 1930s photograph shows signals at Stanmore (controlled from Wembley) displaying Y8LA and Y4LA on the same post. The Y represents Stanmore area control, and the L signifies 'push-pull lever control'. The smaller A denotes platform 1; platform 2 had equivalent numbers with a 'B'.

Code	Control centre or relay room	Current Line (for numbering series purposes)	Date code used (where known)	Became or taken over by (where known)

Luas signals

The only prefix noted (2019) are points indicators on Line B that, logically, carry B. It is thus possible that Line A points indicators carry A.

Manchester Metrolink signals

Originally, on the bulk of the network stop signals did not carry a prefix. Repeater signals carried R. Between Altrincham and Timperley was controlled by the national network signal box at Deansgate Junction with DJ signals in the 500 series. For the remainder of the system, a Network Rail signalling plan uses QR (Queens Road).

The system has received a new control system which has introduced new signal codes. These have a prefix based on the nearby station, and suffix S (stop signals) or P (points indicators). Prefixes known at present are:

Code	Area

Midland Metro signals

Prefixes known are PS (points indicator), S (stop signal), LOS (limit of shunt sign, used without additional number) and SS (stop signal (?), seen near Snow Hill). Level crossing and on-street stop signals do not carry any form of label.

Nottingham Tram signals

Prefixes for these are based on the electrification code, in addition to a P (points indicator) or S (stop signal). Other codes may also exist. Thus a stop signal at Phoenix Park carries the prefix PPS.

Sheffield Supertram signals

It appears that signals are not numbered, being on the whole just tram signals attached to road traffic lights.

Tyne & Wear Metro signals

No evidence of any signal prefix has been found, except on the Pelaw-South Hylton section. This is controlled from Network Rail's Tyneside signalling centre with code T.

Heritage, minor and miniature railways and other 'special' signals

Signal boxes without known prefixes are excluded. Items are shown alphabetically by signal box name or, where there is no known name, by the location.

Code	Signal Box	Location	Note