A £320million programme to lengthen trains on the London Overground has been completed.

Trains on the popular service now can take 170 more passengers, helping to ease congestions on east London routes from Surrey Quays to Shoreditch and Hackney.

Since Transport for London (TfL) created London Overground, passenger numbers on the routes have increased sixfold and the network has become one of the most popular railways anywhere in the country. Spacious, modern carriages are in stark contrast to much of the older Tube rolling stock.

Read more: Re-zoning stations shows east's economic strength

TfL’s director of London Overground Mike Stubbs said: “Over the whole network, we now carry 176million passengers a year, which is six times the number we carried when we took over this railway in 2007.

“The extra carriages that we have now introduced are enabling us to continue to provide our customers with the high quality of safe, reliable and frequent services that they need and expect.

London Overground will be able to carry more passengers on the Gospel Oak to Barking route once the line is electrified, and its diesel trains are replaced with electric trains, in 2018.