Designs for a new generation of Tube trains for London's Piccadilly Line, which will replace the existing 1970s fleet, have been unveiled.
Ninety-four new "fully walk-through" trains with air-conditioning and more space, will replace the 50-year-old stock, Transport for London (TfL) said.
The trains will also be lighter, more environmentally-friendly and future-proofed for a longer life, TfL added.
Plans for new Waterloo & City, Central and Bakerloo line trains are ongoing.
A spokesman for TfL said "despite the devastating financial impact of the coronavirus pandemic", it was honouring the contract signed in 2018 to replace the trains.
The new "Inspiro London" trains, many of which are being built in East Yorkshire by Siemens Mobility, will serve customers on the line from 2025.
"As the new trains are introduced to the Piccadilly Line, the current fleet will be gradually withdrawn from passenger service," a TfL spokesman said.
The frequency of trains in peak hours will rise from 24 to 27 trains per hour from mid-2027.
Andy Lord, managing director of London Underground, said: "The introduction of new, desperately-needed modern and reliable trains on the Piccadilly Line, and the capacity they will provide, will be a boost for the capital.
"We're pleased that our investment in new trains is helping the UK economy and assisting with the recovery from the pandemic, and we look forward to seeing them on the network in years to come.
"Sustained long-term investment would enable us to introduce more modern trains over time to replace other ageing fleets alongside new signalling, improving the journeys of millions more Tube customers and reducing the costs of running the Tube."