First look inside the air-conditioned Piccadilly line trains due through Hounslow and Heathrow

Passengers on the Piccadilly line are getting their first look at the trains that will replace the line's ageing fleet. The new trains have walk-through carriages, wider doors, digital information screens and air conditioning.

Transport for London (TfL) says it is still working to bring the first new train into passenger service between December 2026 and June 2027. The line runs through Acton, Ealing, Hounslow and out to Heathrow, so the trains will become a familiar sight across West London.

Footage shared with UB1UB2 shows the inside of one of the new trains. You can see from one end to the other, with blue grab poles, patterned fabric seats and wide, open spaces by the doors.

What is changing

Siemens Mobility is building the 94 trains as part of the Piccadilly line upgrade. They will replace the 1973 Stock trains that have run on the line for about half a century.

TfL says the new trains offer about 10 per cent more capacity. They have walk-through air-conditioned carriages, wider double doors for easier boarding, real-time digital displays and on-board CCTV. TfL also says they are lighter than the current trains and use about 20 per cent less energy.

Air conditioning is a first for a deep-level Tube line. Passengers on the Piccadilly line's tunnel sections have long complained about the heat in summer. The trains will also send live data about their location and parts to depots, so maintenance teams can spot faults before they disrupt services.

About 80 per cent of the order is being built at Siemens Mobility's Goole Rail Village in East Yorkshire. One of the nine-car trains, about 113 metres long, was on show at the InnoTrans rail exhibition in Berlin from 22 to 25 September 2026. TfL Commissioner Andy Lord was among those who spoke there.

Mixed reactions

Not everyone is won over. Some passengers have questioned the return of fabric seats rather than wipeable ones, and the lack of dedicated luggage space on a line that carries many travellers to and from Heathrow.

An on-board announcement heard in the footage, promising passengers an "exciting journey ahead", has also drawn some amused reactions.

Delays and what happens next

The new fleet is years behind schedule. The first trains were first expected in passenger service in 2024, then by the end of 2025, then in the second half of 2026. TfL has said testing has taken longer than planned. The first unit arrived in London in October 2024.

Several trains are being tested on the network. Old and new trains will run side by side for a while as more of the new fleet enters service.

Work at the line's depots, at Northfields near Ealing and at Cockfosters in north London, will go on into the 2030s. TfL also wants to install a new automated signalling system to run trains more often, but the Mayor's office has said this work is currently unfunded.

For now, passengers in Hounslow, Ealing and Heathrow will have to wait a few more months before they can ride the new trains.