The East London line extension will form part of the London Overground, an orbital railway around London, connecting 20 of London's 33 boroughs.

When the extended line reopens in 2010, it will be part of London Overground rather than London Underground, having been rebuilt to Network Rail standards.

The new East London Line will provide a significantly improved 'Metro' service using larger, longer trains over an extended 25km route running north to Dalston via Shoreditch, Hoxton and Haggerston, and south to New Cross, Crystal Palace and West Croydon.

The West Croydon, Crystal Palace & South Croydon on-network Implementation Works are a fundamental element of the new East London Line. In order to operate as a “Metro” railway, terminus facilities are required at West Croydon and Crystal Palace stations with a turnback facility provided at South Croydon station to accommodate existing train services, currently operated by Southern Trains.

When completed, the new East London Line will operate twelve trains per hour on the northern route, reducing to eight trains per hour on the southern route which runs to Sydenham Spur where the service will then split with four trains per hour travelling to West Croydon and Crystal Palace.

Crystal Palace Station
The station, which was originally opened in 1854 to provide rail access to the Great Exhibition, is a Grade 2 listed building and an excellent example of Victorian legacy.

The works for which Colas Rail is responsible includes the reinstatement of an island platform and associated changes to the permanent way, DC 3rd rail system, signalling & telecommunications and mechanical & electrical works.

West Croydon Station
Providing an important interchange to the Croydon Tramlink and services to London stations, West Croydon station is an important hub that serves a wide community.

In order to accommodate East London Line services, Colas Rail will undertake the extension of an existing platform and undertake alterations to the permanent way, signalling & telecoms, DC 3rd Rail and M&E services.

South Croydon Station
Although not part of the East London Line route, it is necessary to provide a turnback facility at South Croydon which will provide both the East London Line operator and the existing train operator, Southern Trains, with a valuable turnback facility, providing operational flexibility.

As with the principle terminus locations above, Colas Rail will deliver all of the permanent way works, together with the necessary changes to the signalling and DC 3rd Rail system. In addition to the on-site works, Colas Rail will also undertake the alterations to the systems in London Bridge, London Victoria and Three Bridges Signal Boxes.

The extended line is due to open in 2010 with new stations and operating high frequency services that will support the regeneration of some of London's least well-off areas as well as playing a significant part in the transport plans for the 2012 Olympic and Paralympic Games.