\u201cGoing live on Sunday meant that about 1000 members of staff had to be taught how to do something different,\u201d Mr Chris Hobden, London Underground\u2019s Four Lines Modernisation (4LM) project director, told delegates at the Accelerate Rail conference in London on March 19. \u201cSince then we have only had one 20-minute delay.\u201d\r\n\r\nThe 4LM project involves installing Seltrac ATO on the four lines which make up the SSL network: the three others are the Circle, District and Metropolitan lines. The project involves resignalling 310 track-km, 40km of which is underground, five complex junctions, four depots, and 10 train stabling areas. London Underground is also building 46 signalling equipment rooms across the network. A new control centre was completed last year at Hammersmith which will eventually replace 11 signalboxes, one of which dates back to 1926.\r\n\r\nThe SSL network includes joint operation with Network Rail on three sections of line, and with the Jubilee and Piccadilly lines. The project also involves integrating three different Thales Seltrac systems.\r\nCab signalling\r\nThe entire fleet of 192 Bombardier S-Stock trains is being retrofitted with cab signalling. Hobden says it takes 28 days to retrofit one train. London Underground is also installing cab signalling in 33 engineering trains, which takes 30 days per train.\r\n\r\nThe first section to be completed is called phase 0.5 and there are 14 more phases to complete the project. Phases 1-5 cover the Circle Line, sections of which are also used by the other three lines. \u201cIt will be a real challenge to roll it out in central London,\u201d Hobden says. This will be completed in 2020, paving the way for the first increase in train frequency on the SSL network to 30 trains\/hour during peak periods in Central London and to Barking. Train frequency will be stepped up again on these sections in 2022 to 32 trains\/h. The entire network will be fully resignalled by 2023 providing a one-third increase in capacity on the SSL network.\r\n\r\nThe Thales contract is worth \u00a3760m while London Underground is investing a further \u00a3800m in signalling-related works.