Work on the £140m extension to London's Docklands Light Railway (DLR) has begun.
It is estimated 60m people will use the DLR each year by 2005
The line which links the East End to the City is being extended to run out to City Airport and north Woolwich.
It is hoped the 4.4km extension, which will have four new stations, will be completed by late 2005.
The construction project is part of a 30-year £300m design, build and maintenance contract with the CARE consortium - made up of engineering company Amec and the Royal Bank of Scotland.
The project will also include rail links with developments at the Royal Docks and the proposed Channel Tunnel Rail Link station at Stratford.
London's Transport Commissioner Bob Kiley was guest of honour at the ground-breaking ceremony on Tuesday.
"Jobs and prosperity"
Mr Kiley described the extension as "excellent news" for London as a whole.
London's Mayor Ken Livingstone said: "The DLR is at the heart of my plans to regenerate and revitalise Docklands and east London.
"This extension, the first of several planned for the years ahead, means more people will have access to reliable, affordable transport.
"This means more jobs and prosperity for the area."
The Docklands Light Railway was opened in 1987 and carries passengers between Bank, Tower Gateway, the Docklands, and Stratford.
Ten years ago the DLR carried 8.3m passengers per year, that figure has risen to 44m and it is expected to go up to 60m by 2005.
Transport for London has bought 24 new trains for the line at a cost of £40m.
The four new stations will be West Silvertown, Pontoon Dock, London City Airport and King George V at north Woolwich.