Last update 20 November 2020
Additional information is always gratefully received, whether entirely new records (particularly historical records), or information to fill in gaps or correct errors, via the contact link under the Miscellaneous entry in the navigation bar above. Thank you.
Please select a starting letter from the links below:
| Code | Signal Box | Note | ELR | Mileage | Opened | Closed | Control to |
|---|
| OA&GB Junction | MVL1 | 6m 7ch | 1965 | 14 January 1996 | Ashton Moss North Junction (AMN) | ||
| O | Oakenshaw | Formerly named Oakenshaw North | TJC3 | 182m 35ch | 1928 | 23 December 2007 last train; 27 December 2007 official |
Wakefield Kirkgate [new] (WK) |
| OK | Unclear if code carried | ||||||
| ON | Code used when named Oakenshaw North | ||||||
| R | Repeater signals | ||||||
| UM | Up line automatic signals | ||||||
| Oakenshaw North | See Oakenshaw | ||||||
| OA | Oakham | GSM2 | 93m 56ch | 8 October 1899 | |||
| OM | |||||||
| O | Unclear whether code used | ||||||
| OP | Oakleigh Park | ECM1 | ≈8m 25ch | 13 July 1924 | 30 May 1970 | New Barnet (NB) | |
| OT | Oak Tree | DSN1 | ≈4m 28ch | 7 October 1972 | Darlington (D) | ||
| WO | Oatlands | BML1 | 18m 13ch | 1894 | 22 March 1970 | Surbiton [new] (S) | |
| Oddingley | Gate box: line controlled by Gloucester (G) | BAG2 | 62m 61ch | 1908 | |||
| OF | Offord & Buckden | Downgraded to gate box 25 July 1976: line controlled by St Neots (SN) | ECM1 | 55m 76ch | 6 February 1899 | 17 May 1998 | Peterborough (P) |
| OY | Oldbury | Downgraded to shunt frame 8 January 1966: line controlled by Birmingham New Street (NS) | RBS2 | 5m 14ch | ≈28 October 1981 | Birmingham New Street (NS) | |
| Old Dalby NNR | GSM4 | 111m 22ch | ? | ||||
| OM | Oldham Mumps | MPR3 | 7m 21ch | 1967 | 3 October 2009 | Line transferred to Manchester Metrolink | |
| F | Old Kew Junction | HOU | 10m 4ch | 18 October 1942 | 8 September 1974 | Feltham (F) | |
| LG | Old Lea Station | Temporary box intended for occasional use to increase capacity during Nottingham resignalling. Opened and immediately switched out, never used to signal trains. Lincoln to Gainsborough line signals | SPD3 | 95m 68ch | 30 June 2013 | 4 January 2014 | Lincoln Control Centre (LG) |
| OO | Old Oak Common | MLN1 | 2m 64ch | 8 October 1962 | 4 September 1967 | Old Oak Common [new panel] (OO) | |
| EC | Engine and carriage line signals | ||||||
| OO | Old Oak Common [new panel] | MLN1 | 2m 64ch | 4 September 1967 | 30 May 1995 | Slough New IECC (SN) | |
| DG | Down goods and carriage line signals. Code used by 1974 | ||||||
| DM | Down main line automatic signals | ||||||
| DR | Down relief line automatic signals | ||||||
| EC | Engine and carriage line signals. Code used by 1971 | ||||||
| OOO | Code shown in 1984 notice in error | ||||||
| UC | Up carriage line automatic signals | ||||||
| UM | Up main line automatic signals | ||||||
| UR | Up relief line automatic signals | ||||||
| UW | Up Wycombe line automatic signals | ||||||
| Z | Draw ahead signals at Hayes. Code used from 10 August 1983 | ||||||
| C | Old Oak Common Carriage Line Ground Frame | Believed code not carried | MLN1 | ≈2m 0ch | |||
| CR | Old Oak Common Crossrail Depot | Codes shown on development plans | MLN1 | ||||
| DC | |||||||
| WL | Old Oak Common Depot | Wheel lathe line signals | OOC1 | 28 December 2017 | |||
| A | Road A signals | ||||||
| B | Road B signals | ||||||
| C | Road C signals | ||||||
| OT | Old Town | DSN2 | 26 November 1967 | Middlesbrough (M) | |||
| OM | Olive Mount Junction | DSE | 2m 50ch | 1883 | 18 May 1998 | Edge Hill (LE) | |
| OC | Ollerton Colliery | Burnt down April 2006 | HIM | 19m 33ch | 1893 | 23 March 2009 | Thoresby Colliery Junction (T) |
| OY | Onibury | SHL | 22m 68ch | 12 December 1977 | Wales Rail Operating Centre (NS) (planned) | ||
| OL | Ordsall Lane No 1 | Believed code not carried | COL | ≈190m 20ch | 18 October 1978 | Deal Street (DS) | |
| OC | Orgreaves Colliery | Ambiguous source data: colliery branch removed 8 February 1981 | MAC3 | 45m 10ch | 1901 | 8 September 1985 | Darnall West Junction (DW) |
| OW | Orient Way Sidings | Code used from opening | SDC | ≈5m 70ch | 2009 | ||
| JE | Orpington [panel] | Code used from opening | XTD | 13m 49ch | 4 March 1962 | 22 February 1993 | Ashford IECC (AD) |
| JE | Orpington A | Code used from 1959 | XTD | 13m 47ch | ≈1904 | 4 March 1962 | Orpington [panel] (JE) |
| EBV | Otford Junction | Code used from 11 March 1962 | SBJ | 24m 55ch | 1 January 1898 | 5 June 1983 | Victoria Signalling Centre (VS) |
| A | Automatic signals | ||||||
| OB | Oughty Bridge | MAC3 | 36m 23ch | 24 July 1905 | January 1984 | Wadsley Bridge (WB) | |
| OB | Oulton Broad North | NOL | 22m 1ch | 1901 | 24 February 2020 | Colchester [new] (YL) | |
| Oulton Broad Swing Bridge | ESK | 116m 2ch | 1907 | 20 March 2005 | Oulton Broad Swing Bridge [new] | ||
| Oulton Broad Swing Bridge [new] | Renamed Oulton Broad Swing Bridge Operations Cabin 24 February 2020 | ESK | 116m 0ch | 20 March 2005 | |||
| OJ | Over Junction | SWM2 | 115m 53ch | January 1953 | 2 June 1969 | Gloucester (G) | |
| OE1 | Oxenholme No 1 | Code used from 29 April 1973 | CGJ7 | ≈18m 45ch | 12 May 1973 | Carlisle (CE) | |
| OE2 | Oxenholme No 2 | Code used from 29 April 1973 | CGJ7 | ≈19m 5ch | 12 May 1973 | Carlisle (CE) | |
| OX | Oxford | DCL | 63m 46ch | 7 October 1973 | 7 July 2018 last train; 16 July 2018 official |
Thames Valley Signalling Centre (OD) | |
| BT | Signals protecting Bicester London Road level crossing | ||||||
| DM | Down main line automatic signals | ||||||
| DX | Down Oxford line automatic signals | ||||||
| OD | Code shown on some plans, believed never carried | ||||||
| UM | Up main line automatic signals | ||||||
| UX | Up Oxford line automatic signals | ||||||
| OR | Oxford Road | COL | ≈189m 37ch | Manchester Piccadilly (MP) | |||
| OS | Oxheys | CGJ6 | ≈1m 30ch | 3 February 1973 | Preston (PN) | ||
| OY | Oxley | WSJ2 | 143m 14ch | 30 March 1969 | 29 November 2010 | West Midlands Signalling Centre (OS) | |
| CS | Oxley Carriage Shed | WSJ2 | ≈143m 17ch | ||||
| O | Oxmardyke | Gate box: line controlled by Gilberdyke Junction (G) | HUL1 | 16m 22ch | 1901 | 23 November 2018 last train; 26 November 2018 official delayed from 3 April 2018 |
York Rail Operating Centre (GH) |
| OX | Oxmarsh Crossing | BAR | 106m 39ch | 1959 | |||
| OM | Code reported but not seen on site | ||||||
| O | Oxspring Junction | PED2 | 0m 20ch | 1933 | 20 May 1973 | Line closed | |
| CCM | Oxted | Original code phased out 1985-1987 | SCU1 | 20m 32ch? | 1896 | July 1987? | Oxted [new] (OD) |
| OD | New code phased in 1985-1987 | ||||||
| OD | Oxted [new] | SCU1 | 20m 32ch | 11 July 1987 | |||