The long-awaited £3 billion new fleet of Piccadilly line trains remain on course to start running in London in about a year, according to the capital’s transport chief.
Transport for London commissioner Andy Lord said he was “hopeful and optimistic” of hitting the new target of the first trains starting to enter service in the second half of 2026.
Four of the 94 new trains have now arrived in London – though the first one will have to return to the factory for modifications as it was a “prototype”.
Three of the trains have entered testing, which is “going well” and will be ramped up as engineers ensure the trains can be “integrated” with the existing infrastructure on the line, from platforms to signalling.
The first new Piccadilly line train had been due to enter passenger service by the end of 2025.
But the Standard revealed in June that there would be a delay of up to a year.
The new fleet has been purchased to replace trains that are now more than 50 years old, having first entered service in 1973.
But he admitted the delayed introduction of the trains – built by Siemens and assembled at a new factory in Goole, east Yorkshire - was proving “challenging” and was “extremely complicated” to fix.
Mr Lord told the Standard: “I’m really excited about the new Piccadilly line trains.
“Like the new DLR, they are walk-through, air conditioned – the first time ever on the deep Tube – live customer information, capacity enhancements.
“We are doing some really successful testing on the network. They were out again [recently] – we had two trains on the network last weekend [during the partial line closure].
“I’m really hopeful we will continue to make progress for them to be introduced in the second half of next year.
“The trains are going to be absolutely transformational for customers on the Piccadilly line and visitors coming in to Heathrow too.”
The new trains will be the first on a deep-level line to have air conditioning and to be walk-through. This will help to increase capacity on one of the busiest and most strategically important lines on the London Underground.
Many sub-surface Tube trains - such as those on the Circle and District lines - already have air conditioning, as do London Overground and Elizabeth line trains.
“Testing is going well so far, but there is a lot to get through,” Mr Lord said. “Teams are working incredibly hard. Customers and stakeholders will see them out on the network more regularly.
“But we have got to test them, and make sure they can deliver a safe and reliable service. But I’m really optimistic about the significant enhancements.
“Customers will see a real transformation on the line when the trains come into service.
“We have said a window between July and December next year. We are pushing hard for that, and at the minute I’m hopeful and optimistic that we will achieve that.”
The £3.2 billion upgrade of the Piccadilly line was first approved by TfL in 2018.
A paper being presented to TfL’s programmes and investment committee, which meets next week, said that “challenges associated with the design, build and commissioning” of the new trains had been identified.
A “rigorous programme” checking how the train interacts with infrastructure and systems - vital to ensure safety and reliability - was rescheduled to start over the summer.
A review of the total cost of the upgrade is also being undertaken. This will include an updated timeline for the introduction of all 94 new trains – and for the “likely timescale” for increasing the frequency from the current 24 trains per hour to 27 trains per hour.
The report said: “Since July 2025, the first new train has been undergoing testing on the Piccadilly line.
“The first test runs have successfully taken place on the line including running the new train through tunnel sections in central London between Northfields and Hyde Park Corner during a weekend closure on August 2-3.
“Testing is also taking place during the engineering hours period overnight during the week.
“To-date, testing has focussed on the physical interfaces between the train and the London Underground infrastructure.
“This includes train stopping locations, the sighting of signals and signage and measurements at the platform-train interface.
“From the end of September we started system testing, where we start to test the interface with systems that require communication with the train.
“Works continue across the Piccadilly line to enable the infrastructure and systems for the introduction of the new train.
“[This includes] modifications to signalling, power and communication systems, new platform infrastructure, gauging and infringement clearances and works to the depot maintenance and stabling facilities.”
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