An Interlocking machine room (IMR) is a component of the London Underground signalling system. Interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. On the London Underground signals and points are operated and controlled by an array of electrical, pneumatic and mechanical components.[1] IMRs are unmanned and generally located adjacent to points or at platform ends, and provide a secure and weatherproof enclosure for pneumatically controlled mechanically and electrically interlocked levers mounted horizontally in an upright lever-frame or with a converted manual lever frame.[2] [3]
The table below is an alphabetical listing of the extant Interlocking Machine Rooms on the London Underground network in August 2019.[4]
| BB | Queen's Park Depot | Bakerloo | |||
| BD | Paddington | Bakerloo | in middle of platform | ||
| BM | Baker Street | Bakerloo | |||
| BP | Piccadilly Circus | Bakerloo | |||
| BR BS | Waterloo | Bakerloo | |||
| FB | Bromley-by-Bow | District | |||
| FC | Plaistow | District | |||
| FE | East Ham | District | |||
| FF | Barking | District | within manned cabin | FB – FG | |
| FF | Barking Sidings West | District | |||
| FF | Barking Sidings East | District | |||
| FG | Dagenham East | District | |||
| FJ | Hornchurch | District | |||
| FM | Upminster | District | within manned cabin | FJ – FM | |
| FM | Upminster West | District | |||
| JB | Harrow-on-the-Hill North Subsidiary | Metropolitan | |||
| JB | Harrow-on-the-Hill South Subsidiary | Metropolitan | |||
| JE | Willesden Green | Metropolitan Jubilee | |||
| JF | Northwood | Metropolitan | |||
| JJ | Watford South Junction | Metropolitan | |||
| JM MM | Neasden Depot | Metropolitan Jubilee | |||
| JB | Harrow-on-the-Hill | Metropolitan | within manned cabin | JB subsidiaries and JF | |
| JP | Watford | Metropolitan | |||
| JP | Rickmansworth | Metropolitan | within manned cabin | JP, JJ | |
| JT | Chalfont & Latimer | Metropolitan | |||
| JW | Amersham | Metropolitan | within manned cabin | JW, JT | |
| MD | Finchley Road | Metropolitan | was MD JB | ||
| MG JG | Wembley Park | Metropolitan | |||
| MP | Rayners Lane | Metropolitan Piccadilly | With manned Cabin | MU, MW | |
| MU | Ruislip Siding | Metropolitan Piccadilly | |||
| MW | Uxbridge Sidings | Metropolitan Piccadilly | |||
| PB | Green Park | Piccadilly | at end of platform | ||
| PD | Holborn | Piccadilly | |||
| PG | Wood Green | Piccadilly | at end of platform | ||
| PJ | Arnos Grove | Piccadilly | |||
| PK | Oakwood | Piccadilly | inside former cabin | ||
| PM | Cockfosters | Piccadilly | inside former cabin | ||
| VK | Finsbury Park | Victoria | |||
| WB | West Kensington East | District Piccadilly | inside former cabin | ||
| WC | West Kensington West | District Piccadilly | |||
| WD | Hammersmith | District Piccadilly | |||
| WF | Parsons Green East | District | |||
| WF | Parsons Green West | District | |||
| WG | Putney Bridge | District | |||
| WK | Waterloo | Waterloo and City | inside former cabin | ||
| WK | Turnham Green | District Piccadilly | |||
| WL | Acton Town (East) | District | |||
| WL | Acton Town (West) | District | |||
| WM | Ealing Common | District | |||
| WM | Hanger Lane junction | District | |||
| WP | Ealing Broadway | District | inside former cabin | ||
| WR | Northfields Depot | Piccadilly | |||
| WS | Boston Manor | Piccadilly | |||
| WT | Hounslow Central | Piccadilly | |||
| WV | South Harrow | Piccadilly | |||
| WW | Hatton Cross | Piccadilly | at end of platform | ||
| WY | Heathrow Terminals 2 and 3 | Piccadilly | at end of platform | ||
| WZ | Heathrow Terminal 5 | Piccadilly |
| AC | Colindale | Northern | at end of platform | 2008-19 | |||
| AE | Edgware | Northern | inside former cabin | 2008-19 | |||
| B | Kennington | Northern | 2008-19 | ||||
| B | Shoreditch | East London | 2002-08 | ||||
| C | Charing Cross | Northern | inside former cabin | 2008-19 | |||
| CG | White City | Central | within manned cabin | EAB, NOA | 1994-2002 | ||
| E | Camden Town (Platform 1) | Northern | 2008-19 | ||||
| E | Camden Town (Platform 4) | Northern | 2008-19 | ||||
| EAB | Ealing Broadway | Central | 1994-2002 | ||||
| ET | Canal Junction (south of Surrey Quays) | East London | within manned cabin | 1994-2002 | |||
| ET | New Cross Gate | East London | 1994-2002 | ||||
| F | Hampstead | Northern | inside former cabin | 2008-19 | |||
| G | Golders Green South | Northern | 2008-19 | ||||
| G | Golders Green North | Northern | 2008-19 | ||||
| HON | Holborn | Central | 1994-2002 | ||||
| JL | Stanmore Sidings | Jubilee | 2008-19 | ||||
| LB | Liverpool Street | Central | in manned cabin in middle of platform | 1994-2002 | |||
| LC | Bethnal Green | Central | in manned cabin in middle of platform | 1994-2002 | |||
| LF | Leytonstone | Central | in manned cabin | 1994-2002 | |||
| LJ | Woodford | Central | in manned cabin | 1994-2002 | |||
| LL | Hainault | Central | in manned cabin | Also controlled LL Grange Hill subsidiary area | 1994-2002 | ||
| LP | Newbury Park | Central | in manned cabin | 1994-2002 | |||
| LT | Loughton | Central | in manned cabin | 1994-2002 | |||
| LU | Debden | Central | in manned cabin | 1994-2002 | |||
| LW | Epping | Central | in manned cabin | LW, LX | 1994-2002 | ||
| LX | North Weald | Central | in former manned cabin | 1994-2002 | |||
| M | Moorgate | Northern | inside former cabin | 2008-19 | |||
| MAA | Marble Arch | Central | 1994-2002 | ||||
| NN | Archway | Northern | inside former cabin | 2008-19 | |||
| NOA | North Acton | Central | 1994-2002 | ||||
| NOR | Northolt | Central | at end of platform | 1994-2002 | |||
| NP | East Finchley | Northern | inside former cabin | 2008-19 | |||
| NQ | Finchley Central | Northern | inside former cabin | 2008-19 | |||
| NU | High Barnet | Northern | inside former cabin | 2008-19 | |||
| OP | Edgware Road | Metropolitan | within manned cabin | 2008-19 | |||
| OZ | Hammersmith | Metropolitan | within manned cabin | 2008-19 | |||
| QUE | Queensway | Central | at end of platform | 1994-2002 | |||
| RUG | Ruislip Gardens | Central | 1994-2002 | ||||
| TF | Green Park | Jubilee | 2008-19 | ||||
| TG | Charing Cross | Jubilee | at end of platform | 2008-19 | |||
| U | Stockwell | Northern | 2008-19 | ||||
| VE | Brixton | Victoria | at end of platform | 2008-19 | |||
| VF | Victoria | Victoria | at end of platform | 2008-19 | |||
| VG | Warren Street | Victoria | at end of platform | 2008-19 | |||
| VH | King's Cross St Pancras | Victoria | at end of platform | 2008-19 | |||
| VJ | Highbury & Islington | Victoria | 2008-19 | ||||
| VL | Seven Sisters | Victoria | 2008-19 | ||||
| VN | Northumberland Park Depot | Victoria | 2008-19 | ||||
| VP | Walthamstow Central | Victoria | at end of platform | 2008-19 | |||
| W | Tooting Broadway | Northern | at end of platform | 2008-19 | |||
| WER | West Ruislip | Central | within manned cabin | WER, RUG, NOR | 1994-2002 | ||
| X | Angel | Northern | in former manned cabin at end of platform | 1994-2002 | |||
| Y | Morden | Northern | 2008-19 | ||||
| EN | Whitechapel | District | within manned cabin | 2021 | |||
| EC | Earl's Court | District | at end of platform | 2022 | |||
| ED | High Street Kensington | District | 2022 | ||||
| ED | Triangle Sidings (Kensington) | District | 2022 | ||||
| EE | Gloucester Road | District | 2022 | ||||
| EF | South Kensington | District | 2022 | ||||
| EG | Mansion House | District | 2021 | ||||
| EH | Embankment | District | at street level | 2021 | |||
| EJ | Tower Hill | District | in middle of platform | 2021 | |||
| MB | Baker Street | Metropolitan | under platforms 1 & 2 | 2019 | |||
| ML | Swiss Cottage | Metropolitan | 2019 | ||||
| OB | Aldgate | District Metropolitan | 2021 | ||||
| OD | Liverpool Street | Metropolitan | inside former cabin | 2021 | |||
| OE | Moogate | Metropolitan | 2021 | ||||
| OH | Farringdon | Metropolitan | 2021 | ||||
| OJ | King's Cross St Pancras | Metropolitan | at end of platform | 2021 | |||
| L | King's Cross | Northern | inside former cabin | ||||
| J | Euston | Northern |