55 carriages also given improved interior.
The first of a fleet of new Docklands Light Railway (DLR) three-carriage trains have gone into public service.
An extra carriage is being added to trains on the Bank to Lewisham route and will provide 50 per cent more space for passengers. The route serves stations including Canary Wharf, Greenwich and Limehouse.
A £325 million two and half year upgrade programme has taken place across the DLR network to allow the longer trains to run.
The programme includes lengthened platforms, a new £22 million South Quay station, upgraded track and infrastructure, including innovative junctions that allow two trains to pass simultaneously and a £13 million upgrade to Tower Gateway station, including new canopies and energy efficient escalators
55 new carriages also have improved interior layout to give more room and easier exit and entrance.
Upgrades have been completed on all parts of the DLR network aside from the Canning Town to Beckton route, which will be ready in early 2011. Three car trains will be rolled out across the network as demand requires.
Jonathan Fox, Director DLR, said: "This marks another major milestone for DLR and its passengers as our network is further enhanced and improved."
"With three-car trains being rolled out on the Bank-Lewisham line, and the Stratford International extension set to open later this year, we are in great shape to meet passenger demand now and over the course of the next few years."