The London Underground 2024 Stock (also known as the New Tube for London) is a new fleet of Siemens Mobility trains built in the UK and Austria, designed to modernize the deep-level lines. An initial order of 94 nine-car trains, costing £1.5 billion, will replace the aging 1973 Stock on the Piccadilly line, with options for up to 250 trains to eventually replace fleets on the Bakerloo, Central, and Waterloo & City lines. The first train arrived for testing in London in October 2024, and the fleet is scheduled to enter passenger service between December 2026 and June 2027. These trains feature walk-through carriages (open gangways), air conditioning, and are lighter and more energy-efficient, offering greater passenger capacity than the older deep-level trains they replace. While initially planned to be driver-operated, the design allows for future driverless operation, a prospect strongly opposed by the ASLEF and RMT unions, which also requires costly platform screen doors. The project follows the collapse of the public-private partnership (PPP) in 2010, after which Transport for London (TfL) took direct control of modernizing the network.