We are transforming the Circle, District, Hammersmith & City and Metropolitan lines. When the work is completed in 2023, increased capacity and boosted reliability will make journeys faster and more comfortable.

Because these lines share a lot of track and infrastructure, they are being modernised under a single combined and integrated project, Four Lines Modernisation (4LM).

Watch how we're transforming the Circle, District, Hammersmith & City and Metropolitan lines.

The four lines are among some of the oldest sections of the Underground network, with parts dating back to 1863. Together they make up 40% of the Tube network, with around a million passenger journeys each day. Geographical map of the four lines PDF 211KB Some equipment used on these lines is old and needs to be replaced. We're introducing new technology that will reduce journey times and increase capacity - essential to support London's growing population. This project will require some line closures. To stay up-to-date you can follow @TfLTravelAlerts on Twitter, check Journey Planner and sign up to our email alerts.