Marble Arch signal cabin

Marble Arch
CD
Overview
Opened	30 July 1900
Closed	9 December 1999
Operator	London Underground

Marble Arch (prefix CD) was a signal cabin located within the station of the same name on London Underground's Central line. Opened in 1900, replaced in 1956 and closed in 1999, the 1956 lever frame has been preserved and restored as a demonstrative exhibit at London Transport Museum, Acton Depot.

Central London Railway

Marble Arch opened on the inaugural section of the Central London Railway (CLR) between Bank and Shepherd’s Bush on 30 July 1900. The CLR was part of the growing number of lines in London built at a Deep-Level following on from the City & South London Railway (1890) and the Waterloo & City Railway (1898). Because it was slightly later in development, the CLR benefited from a more modern design ethos ranging from the spacing of stations to the inclining of station approaches to aid headways and the provision of additional crossovers and sidings as turnback points.

The signal cabin at Marble Arch (prefix D) was provided to control one such east facing siding and was equipped with a full size mechanically interlocked Evans O’Donnell frame of 17 levers. The next signal cabin west was Queensroad ( renamed Queensway in 1946) and east at British Museum both of which controlled similar layouts to Marble Arch.

London Transport

In 1940, the tunnels built by the CLR were widened to bring them closer to what was evolving into a standard 12 ft tunnel diameter for all Deep-Level lines incorporated into London Transport. Despite this effort to standardize which included the adoption of the 4^th rail set up for powering trains, several design traits from the CLR remained most notably in stations and track layouts which were largely untouched. Marble Arch signal cabin similarly remained untouched during this period apart from a re-lettering to prefix CD.

In 1956, the signal cabin was re-equipped with a Westinghouse N-style electrically interlocked miniature lever frame of 11 levers. Whilst the technology that would supersede lever frames already existed by this point, the comparatively small geographic coverage that was a common trait of Deep-Level signal cabins meant that lever frames still represented good value for money. The signal cabin spent the rest of its operational life virtually untouched.

Closure and Preservation

By the 1990’s, the signalling on the Central line was deemed to be life expired and was becoming increasingly unreliable to support the ever more intensive service patterns needed to meet growing patronage. With the introduction of the 1992 stock, London Transport developed a fully integrated Automatic Train Operation system in house using off the shelf components supplied by Westinghouse. This computerised system transmitted commands from a network of Signal Equipment Rooms (SER) to computers on board trains giving movement authorities as well as brake and coasting commands. This dispensed with the need for auxiliary train protection and signal cabins and forms the basis for modern Automatic Train Operation (ATO) to this day.

The migration between legacy signalling and ATO was split into stages the first of which involved decommissioning all existing signal cabins and using the new SER’s before ATO was commissioned. In lieu of this, the miniature lever frame was taken out of use on 10 January 1994 being superseded by a temporary Westinghouse relay interlocked Push Button Desk. This lasted until 9 December 1999 when ATO was commissioned, and the signal cabin was officially closed when control passed to Wood Lane service control centre.

Having remained in situ for several years in the disused signal cabin, the N-style miniature lever frame was dismantled and brought to London Transport Museum, Acton Depot for restoration circa 2009. It now operates as a demonstrator exhibit simulating the operation of a typical through station with multi-home signalling, track circuits, train describers and route setting.