The East London Line will have 12 trains an hour
Full evening and weekend services have begun on the new East London Line.
Twelve trains an hour will run from Dalston Junction, north London, to West Croydon, New Cross and Crystal Palace in south and south-east London.
The route, which is a part of London Overground network, is the first phase of a £1bn extension of the line.
Local residents in Penge West are holding a party next to the new station to celebrate the Tube network coming to the area.
Rise in passengers
Trains will travel through Whitechapel station and Shoreditch High Street, a main Zone 1 station.
Before the extension the line carried nine million passengers every year, but this is expected to rise to 33 million by 2011 and rising to 40 million by 2016, Transport for London said.
A "preview" service of eight trains an hour began running between New Cross Gate and Dalston Junction from 27 April.
Engineering works are continuing to extend the East London Line to Highbury and Islington by spring 2011.
An extension of the line to Clapham Junction, in south-west London, is planned by 2012.
The line will form part of a planned wider London Overground orbital network, which will allow passengers to travel around London on the line without having to enter central areas of the city.