From levers and buttons to computer screens

Tuesday 14th July 2026

Signal boxes are becoming something of an endangered species on the railway, not least on the London Underground, with modern technology enabling trains to be controlled from a computer screen many miles away from the tracks and in-cab displays for drivers rather than what is now regarded as old fashioned track side signals managed by staff from stand-alone signal cabins.

Despite the gradual phased roll out of Computer Based Train Control (CBTC) on the sub-surface London Underground lines over the last few years traditional signal cabins can still be found on the outer reaches of the Metropolitan line at Harrow-on-the-Hill, Rayners Lane, Rickmansworth and Amersham.

However their days are now very much numbered with CBTC almost ready for switch on in this section too so it was a delight to be able to pay a visit to both Rayners Lane and Harrow-on-the-Hill signal cabins last Thursday as part of a tour organised by the London Transport Museum Friends to see the ‘old style’ of signalling in action.

The signal cabin at Rayners Lane is situated at the western end of the London bound platform offering a bird’s eye view of the station platforms and the track towards Uxbridge including the centrally located turn-back siding. The cabin’s origins can be traced back to 1904 when a small lineside shack controlled the section of track through to Uxbridge with Rayners Lane station itself opening two years later, initially as Rayners Lane Halt. By 1910 the junction east of the station was built, originally to connect to the site of a Gas Works and the then District line, which arrived from Acton Town, later to become the Piccadilly line.

Metroland famously came along in the 1930s which saw considerable expansion including a new station and signal cabin opening in 1935 together with cabins at Ruislip and Uxbridge. Changes in recent decades have seen the Rayners Lane cabin cede control of the sidings at South Harrow to the Piccadilly line control centre based at Earls Court as well as both Ruislip and Uxbridge cabins closing in 1978 and 1985 respectively with control moving to an expanded Rayners Lane while in 1986/87 push buttons replaced the previous lever frame method of operation. Nowadays replacement parts for the forty year old console are getting harder to source as the date draws near for the transfer to CBTC.

Track side displays are installed and ready for the new system but are currently covered over with black bin liners and white tape. Another tell tale sign are small yellow sensors attached to the tracks…

… which enable the mew system to know the exact location of trains, to within six centimetres at critical locations.

The great benefit of CBTC comes from enabling trains to travel closer to one another making frequency increases in timetables a realistic proposition compared to the conventional method of signalling.

For now, signallers at Rayners Lane rely on large traditional style wall mounted screens showing each train’s location in relation to station platforms, signals and junctions by coloured lights with buttons pressed manually on the console to clear the path or hold the train, as required, at each signal.

As you can see from the above photograph of the display, the Rayners Lane cabin controls the track from east/south of the junction between the Metropolitan and Piccadilly lines through to the terminus at Uxbridge including the centrally located turn back siding at Rayners Lane, regularly used by Piccadilly line trains, the northwestern entrance/exit to the sidings and engineering depot at Ruislip used by Central line and engineering trains and all the sidings at Uxbridge as well as the intermediate stations at Eastcote, Ruislip Manor, Ruislip and Hillingdon making for quite a workload for the signaller, especially if things don’t always go to plan.

It was fascinating to hear from manager ‘TD’ as well as watch duty signaller Trevor describe the workings of the cabin and it was obvious how much they enjoyed their work with enthusiasm and dedication as well as ensuring safety is the overriding principle behind all decisions.

After that visit it was a short ride on a Metropolitan line train down to Harrow-on-the-Hill where our small party of eight visitors found the anonymous ‘red door’ at the northern end of Platforms 3 and 4…

… through which a never ending staircase took us up high above the station platforms into the cabin.

The layout is similar to Rayners Lane with a large traditional style display on the wall, except here the reverse arrangement applies with unoccupied sections of track being lit and train locations shown by the lights turning off.

As you can see the track covered by the cabin stretches from south of Harrow-on-the-Hill through to Moor Park on the line towards Rickmansworth including North Harrow, Pinner, Northwood Hills and Northwood stations…

… and many crossovers and the junction and tracks heading towards Uxbridge. It also includes control of the tracks used principally by Chiltern Trains on the Marylebone to Aylesbury line. To the left of these boards is a display…

… which highlights the codes of each train approaching the section of track being controlled by the signaller.

However, the main difference to Rayners Lane is the continued use of levers rather than buttons to control the signalling as can be seen in the console in front of the displays on which there are just under 100 levers in a long line making it the largest signal cabin of its kind in the UK.

One reason for so many levers is this cabin also now does the work of what were once two further signal cabins to the south and north of Harrow-on-the-Hill. These are still in situ with their levers all working but they’re now remotely controlled by this main signal box high above Harrow-on-the-Hill station.

It makes for a mind-boggling array of levers and you can’t fail but admire the professionalism of the signaller on duty who just took it all in his (and then her) stride as the team swapped over for the late shift during our visit. During last week’s exceptionally hot weather special arrangements were in place to minimise risks of track damage by avoiding using the crossovers wherever possible and restricting trains to the tracks they were already on. This meant the fast peak hour Metropolitan line trains were restricted to follow the all-stations trains rather than cross over to the tracks used by Chiltern Trains.

The visit was managed for the London Transport Museum Friends by Charley who has been a signaller and is now involved in training colleagues in the skills required. Charley’s enthusiasm and passion for the job was obvious as she described the workings of the cabin to us and as a bonus concluded the visit by a look at the Relay Room on the floor below.

This houses all the electrical equipment that works the signals, points and stations displays out on the line and is part of the infrastructure which will become redundant in the upcoming months when the switch over to CBTC occurs. I got the sense the team will be sad to see all this go, they’re part of what is obviously a very friendly ‘family’ style of team working, but also a realistic recognition of the inevitability of technological progress. Charley for one, I can see, will be keen, along with the London Transport Museum, to preserve aspects of this tradition that’s coming to an end, so that it will be available for future historians and those with an interest in railways.

A fabulous visit and thanks to the London Transport Museum Friends and Charley for laying it on.

Roger French

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