TRANSPORT FOR LONDON’S HEAD OF 4LM CHRIS HOBDEN UPDATES PHILIP SHERRATT ON PROGRESS WITH UPGRADES TO THE SUB-SURFACE LINES
The Four Lines Modernisation (4LM) is a large and complex programme. The Circle, District, Hammersmith & City and Metropolitan Lines comprise 40% of the London Underground (LU).
But the size of the network is not the only cause of complexity – there are shared tracks with Network Rail routes and other tube lines, along with a series of complex junctions within the central area. And the programme involves modernising the oldest underground routes in the world.