London Underground’s largest signalling upgrade project, 4LM, has reached a milestone moment in its deployment.

The project, which covers 113 stations, 193 miles of track across four underground lines, Circle, District, Hammersmith & City and Metropolitan Lines, covers 40% of the London Underground network. It is one of the most complex signalling projects on a metro system anywhere in the world.

The latest work has covered the lines near Neasden depot, where the integration between two different control systems designed ten years apart had to be seamlessly brought together to avoid major disruption on a number of Underground Lines.

“This milestone showcases not only the technical strength of our systems, but the people and partnerships that made it possible. It’s a story of precision delivery and exceptional teamwork.”

Andy Bell, Vice President, Hitachi Rail UK

The Communications-Based Train Technology (CBTC), designed by Hitachi Rail, has brought together the Jubilee Line’s SelTrac™ system and the legacy interlocking infrastructure.

Bringing together two different systems like this enables Transport for London to expand the CBTC signalling across more of the underground network in future, enabling frequent services and reliability, especially where trains from two different Underground lines share the same running lines in London.

This completion of the work at Neasden Depot marks a key moment in deploying the latest CBTC technology to one of the world’s most heavily used transport systems.

“Delivering this phase demanded live system switching, real-time data synchronisation, and coordination across multiple lines, all with minimum disruption to operations. It’s a testament to the capability of our teams and our close collaboration with TfL.”

Clarke Walker, Project Director, Hitachi Rail UK

CBTC has been used by Hitachi to bring together various railway operating systems across the globe. Back in January, it was used in part to deliver Madrid’s first driverless metro railway, while in Australia last summer, the system was deployed in Perth, making it the third city in Australia to install the technology.