Signal box prefix codes

A (hopefully) comprehensive listing

'Boxes beginning U

Last update 27 July 2021

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
U Uddingston Junction WCM2 93m 44ch 27 June 1937 18 September 1973 Motherwell (M)
UN Uffington PMJ 12m 74ch 26 June 1909
U Uffington MLN1 66m 42ch 1897 3 March 1968 Swindon (SN)
DM Down main line automatic signals
UM Up main line automatic signals
UC Ufton Crossing BHL 43m 39ch 14 February 1943 3 December 1977 Reading (R)
UJ Ulceby Junction Formerly named Ulceby South Junction BRI1 100m 32ch 1910 30 December 2015 York Rail Operating Centre (CB, MB)
UY Code used with semaphore signals
D Down line automatic signals
U Up line automatic signals
Ulceby South Junction See Ulceby Junction
UN Ulverston Code used from 2008 CBC1 19m 47ch 16 December 1900
UC United Colliery WSJ2 203m 56ch 9 August 1970 1 October 1974 ultimately Chester PSB (CR)
UCR Distant signals
UC Unstone Colliery Sidings TJC1 149m 68ch 15 January 1972 Dore (D)
Uphill Junction MLN1 138m 6ch 1884 29 January 1972 Bristol (B)
UM Upminster FSS2 15m 38ch 17 April 1995 Upminster IECC (UR)
D Down line automatic signals
U Up line automatic signals
UR Upminster IECC FSS2 15m 38ch 11 September 1994 6 December 2019 (planned) Romford Rail Operating Centre (UR) (planned)
NL North London Line signals. Code used from 4 January 2011
UGF Ground frame controlled signals
UE Upminster East FSS2 UPG 15m 44ch 0m 5ch ? ≈1995 Upminster IECC (UR)
UW Upminster West FSS2 15m 15ch ? 6 February 1961 Upminster (UM)
UY Upney FSS2 8m 9ch 27 March 1961 Barking (BK)
M Upper Abbey Mills Junction FSS1 3m 61ch 1 May 1961 Fenchurch Street (F)
UH Upper Holloway TAH1 2m 76ch 10 November 1985
CCH Upper Warlingham SCU1 15m 30ch 10 March 1884 2 November 1985 Three Bridges [new] (T) and Oxted (OD)
U Upton Park FSS1 5m 37ch 1 May 1961 Barking (BK)
UN Urlay Nook Downgraded to gate box 25 November 2013: line controlled by Bowesfield (B) DSN1 7m 38ch 1896 11 March 2019 York Rail Operating Centre (B)
R Distant signals
US Usan Code used from 2002 ECN4 28m 48ch 6 May 1906 2 February 2010 delayed from 28 January 2008 Montrose North (MN)
UH Usworth Code used from 24 April 1982 FEP 17m 45ch 1898 1991
U Uttoxeter Two signals only. Last all-new mechanical 'box NSS 16m 0ch 28 January 1981
UR Code used from 2 January 2008