The new East London Line has been opened to the public, forming part of the London Overground network.
A "preview" service of eight trains an hour will run between New Cross Gate and Dalston Junction, between 0700 BST and 2000 BST, from Monday to Friday.
Full evening and weekend services will begin on 23 May, when 12 trains will run each hour.
Trains will travel through Whitechapel station and Shoreditch High Street, a flagship Zone 1 station.
London Mayor Boris Johnson, who officially opened the route, said: "This new railway will bring jobs and opportunities to communities up and down the line, massively improving access for hundreds of thousands of people.
"This type of investment is essential if London, throwing off the shackles of recession, is to emerge with the ability to grow, prosper, and secure its position at the summit of world cities, to the benefit of all Londoners."
Do you need a station?
Oyster cards can be used on the new trains which have no doors separating the carriages, allowing passengers to walk the length of the train.
The opening is the first phase of a £1bn extension of the line.

