Barber and Osgerby – designers of the London 2012 Olympic Torch – won the tender to create the interior, exterior and livery for the trains that will be used on the Crossrail line, a new cross-capital railway due for completion in 2017.
"Crossrail presents us with a historic opportunity to create a design legacy for London," said the designers. "London is the city that we both live and work in and we feel proud to have won this project. It gives us the chance to make a profound contribution to millions of commuters."
The duo will work with Transport for London (TfL) and UK train manufacturer Bombardier to design and build the trains. Each will be made up of nine carriages, measure just over 200 metres long, and capable of carrying up to 1,500 passengers.
Once complete, the Crossrail line will provide a new west-east link through central London, connecting Reading and Heathrow with Shenfield and Abbey Wood through tunnels beneath the city.
The line will connect with the existing London Underground and London Overground networks at a number of stations along its length, and will be coloured light purple on the city's iconic Tube Map.
"Following a competitive process, we are delighted to have appointed Barber & Osgerby to work as our design partner on the Crossrail trains," said TfL head of design Jon Hunter. "Without doubt, their vision and forensic approach to design will help ensure that the new trains will be iconic and befit London's newest rail line."
Barber and Osgerby have previously designed a £2 coin to commemorate the 150th Anniversary of the London Underground and are creating a "gigantic scale" rotating sculpture to be installed inside the V&A Museum during this year's London Design Festival.
Their Olympic Torch was awarded the Design of the Year by London's Design Museum in 2012.
Thomas Heatherwick, who designed the cauldron for London's Olympic Games, is also working with TfL on a number of transport projects. Having completed the new Routemaster bus in 2011, he has most recently put in an informal bid to work on the extension of the Underground's Northern Line.
Other designers who have worked on rail projects include Kenneth Grange, whose 1976 InterCity 125 train is still in use on British rail lines.
More conceptually, PriestmanGoode revealed a proposal for high-speed trains that would transfer passengers to local services while still moving, instead of stopping at stations.