The East London line extension (ELLX) project is a British railway engineering project in London, managed by Transport for London. The project involves extending the East London Line (formerly part of the London Underground network) and making it part of the mainline London Overground network. This is being done by re-opening sections of disused railway line and by converting track electrified by the third-rail system, signalling, lineside signage and communication systems, etc. to mainline standards. New rolling stock was introduced and four new stations built along the route, with possibly a fifth to be added later.