With the decline of coal traffic and the closure of the Bute Docks, it now sees only passenger services, and connects the Cardiff Bay neighbourhood to the other Valley Lines.

[4] On 16 July 2012, plans to electrify the line were announced by the government, as part of a £9.4bn package of investment of the railways in England and Wales.

[7][8] A new station would be constructed at Loudoun Square and a short extension would be built taking the line closer to Cardiff Bay, opening in December 2023.

[9] In August 2022 it was announced that the existing Cardiff Bay station would now be retained (with no extension built) and it will get a second platform as well as a new signage and customer information screens.

The station at Loudoun Square will now be located further north than previously planned (near Maria Street) and would also comprise two platforms, opening in spring 2024.

Preliminary construction on both Butetown and the redevelopment of Cardiff Bay began in January 2023 with the main works to begin later in summer 2023.