Railway Signalling Centre

Three Bridges, Sussex – 9th May 2007

A good size party of 18 members and 5 guests assembled in the Booking Hall of Three Bridges Rail Station for this morning visit. It was arranged by Roger Penny, who spoke to the RCEA in December 2006 on Railway Signalling Infrastructure. The party was guided by Roger, and Nick Whiting from the Signalling Centre.

The Centre, readily visible to passengers travelling through the station, was entered through security entrances at the end of platform 5. The Centre, built in 1984, controls rail traffic broadly from Selhurst to Brighton. The large brick building was on two levels, the lower one supplying information to the upper Signalling Centre Display Room.

The lower room was toured first. It was fully automated, during our visit there were no personnel working in the room. The first section seen consisted of banks of relays set in rows, each relating to a labelled local area. The banks were lit, different colours indicating local line status. The relays were large and designed for rail data use, employing carbon­silver contacts. The Centre controlled all rail points settings, and level crossings. Safety interlocking was controlled at the local level. Some settings in open countryside were controlled automatically from rail line signals. Contact with train drivers was by radio or telephone, including secure satellite technology. Telephone lines were duplicated, and laid along separate routes, in the event of failure of one line. Power for this area was backed up by batteries for periods of peak loading.

The Train Describer Area provided a unique 4-digit code for each train. In this area an old computer hard disk was seen, measuring some 14inches diameter by 1inch thickness, with a capacity measured in kilobytes (compare this to modem hard disks). In 2005, a modem computer system was installed, including double power supplies for back up. Data from the computers in the lower area was recorded and stored, in the event of future investigation. It was noted that experience had shown the computers to be very reliable, associated problems mainly originating from the rail track due to the hostile environment. This resulted in maintenance and signal cleaning on the track. (Refer to Newsletter Report Dec.2006, ppI4/15)

The upstairs Signalling Display Room was dominated by a panoramic view of the track and train display for the region covered, Selhurst to Brighton. Each train, identified by its 4-digit code, had its position displayed and its journey progressed by a series of coloured lights. Separate was a second, smaller modern, display, which covered the Horsham to Billingshurst area. This activity was controlled by approx. 1-dozen staff, 24 hours per day, each controller responsible for their own area. An important safety factor was track temperature. When this exceeded 40 degrees C, train speeds were reduced. This check was currently manual but would soon be automated and controlled ftom Three Bridges.

The interest shown by the visit was reflected in the party size and the questions and discussion, virtually continuous throughout. Roger and Nick received a well-deserved vote of thanks from Glyn Mathias.

C Harrison