Too Complex for a Computer

Borough Market Junction was a traffic bottleneck. Six running lines flowed from London Bridge and diverged into four lines for Cannon Street and two for Waterloo East and Charing Cross. The core of the problem was the conflict of trains heading into Cannon Street and out of Charring Cross. In the early 1960’s the demise of steam seemed to offer a window of opportunity to increase the flow of trains over this crowded junction and resolve these conflicting moves.


by the early 1960′s steam was on a clear road to the scrap yard.


Using steam locomotives generated many light engine movements; as engines ran round their trains, shunted carriages and went to coal, water and turn round. Replace steam with electric multiple units and at a stroke, you create new train paths; paths that could be used to strengthen peak services. With a change of terminal destination departures at key moments; so Charring Cross trains did not conflict with Cannon Street services, Borough Market Junction could handle even more passenger trains.


Its was just to0 complex to computerise


Now could engineers make train operation even more efficient at Borough Market Junction, by replacing its human signallers with a computer system? Could the white heat of 1960’s computer technology transform Britain’s busiest Signal box? In short, no; after 18 months investigation the Divisional Engineer declared ‘no computer so far devised could be programmed so as to replace in rapid and alert action the skill of the signalmen at Borough Market Junction.’

Filed under: Conservation

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It ought to be pointed out that the majority of trains in the 1960s were already EMUs. The Kent coast electrification of the late 1950s significantly reduced steam haulage, although not eliminating it completely, of course, since the Mid-Kent line and others were not yet fully electrified.

But the routes conflicts remained. As a commuter through London Bridge 1969-1977, I experienced the massive resignalling and rebuilding of the through station in the early 1970s, in which many of the conflicting moves were eliminated by, as far as possible, separating Cannon Street and Charing Cross trains as far East of London Bridge as could be arranged. This was done even to the extent that the Lewisham-Nunhead line was adapted to provide a flyover at St Johns so that Charing Cross trains running through Lewisham station could be taken over the Mid-Kent line and onto the 'fast' lines, now destined to be the Charing Cross lines, or trains from Charing Cross could be crossed over to get to Lewisham with minimum conflict. A very interesting time!

The new signal box at London Bridge covered the whole of the lines from Charing Cross, Cannon Street and London Bridge itself, although I am uncertain how far out their control area went.