London Bridge station is the fifth busiest in the country, handling nearly 40M passengers a year.
With the development of Thameslink 2000, through traffic will increase considerably.
Redevelopment of the station, which is being designed by Alan Baxter Associates will include a new concourse below the tracks, to serve as both terminus and through platforms. The new station will provide nine through platforms and six terminating - at present the station has nine terminating and six through.
Platforms are to be widened, to cope with the increased passenger numbers and less sharply curved. Wide escalators will transfer people between the platforms and the mezzanine.
A unique trestle will support the deck of the air right development above the station.
The supports will reach up 'like fingers' through the station to spread loading, and reduce the depth of deck structure required.
The station is scheduled to remain open during the works.