A new rail network for London has been officially launched by the Mayor of London Ken Livingstone.
London Overground line will take over routes from Silverlink
London Overground (LO) has taken over the suburban routes previously operated by Silverlink which include the North London Line and West London Line.
Passengers have been assured of "immediate improvements" with the introduction of Oyster pay-as-you-go facilities and greater staffing levels.
Services on the new network began on Sunday morning.
Network Rail owns some of the stations which are leased to Transport for London (TfL). TfL owns the rest.
London Overground Rail Operations Limited (Lorol) will run the services on behalf of TfL.
Lorol, which has a seven-year contract with TfL, is jointly owned by Hong Kong firm MTR and construction firm Laing.
TfL is planning more than £1.4bn of investment, including more staff, refurbished stations, CCTV, and better lighting systems.
The other routes covered by the network are Gospel Oak to Barking and Euston to Watford.
A total of 44 electric and air-conditioned trains, costing £223m, will replace the Silverlink trains from the end of 2010.
The brand complements the Underground logo
That same year, LO services will also operate on the extended East London Line, which will run from Dalston Junction to West Croydon, Crystal Palace and New Cross, when it opens.
In 2011 the line will be connected to the North London line at Highbury and Islington, creating the first step towards an orbital service.
A TfL spokesman said: "Passengers will notice immediate improvements from day one with the introduction of Oyster pay-as-you-go facilities and stations staffed at all times trains are running."
Mr Livingstone said: "London Overground, giving Transport for London control of key parts of the overground rail services in the capital, is the start of a radical revitalisation of London's rail services. which have suffered from decades of neglect and under-investment."
But Rail, Maritime and Transport Workers union (RMT) said safety of passengers could be compromised.
RMT general secretary Bob Crow said: "We believe that safety will be undermined by unnecessary fragmentation, with two organisations responsible for signalling, two for infrastructure maintenance, two for infrastructure renewals, one for train and station operations and another for train maintenance."
A spokesman for TfL said the RMT's claims were "rubbish".