The work is part of the £320m London Overground Capacity Improvement Programme (LOCIP) to deliver an additional 25% capacity.
The longer platforms will accommodate longer trains, which are being increased from four to five carriages. The first of these longer trains will run on the Highbury & Islington to New Cross/Crystal Palace/West Croydon/Clapham Junction routes from the end of 2014, followed by the Clapham Junction/Richmond to Stratford routes by the end of 2015.
Work at the first London Overground stations on the Clapham Junction/Richmond to Stratford route is expected to begin in February 2014 while work on the Highbury & Islington to New Cross/Crystal Palace/West Croydon/Clapham Junction routes will begin later this month.
Platform extensions on the Highbury & Islington to New Cross/Crystal Palace/West Croydon/Clapham Junction routes are being carried out under a separate contract with Cleshar Contract Services.
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