Transport for Wales is urging all customers to check before they travel as South Wales Metro works will impact services from next weekend.
Transformation works will continue across the valley lines in preparation for the South Wales Metro and its connecting lines.
The first of several engineering works affecting services through Cardiff Queen Street will begin over the August bank holiday weekend and will take place intermittently through to November.
TfW is advising all customers to check before they travel as rail replacement buses will be in operation.
Information posters will be displayed at stations across the affected lines and journey checker will be updated to inform customers.
The transformation of the Core Valley Lines for the Metro has been part-funded by the European Regional Development Fund through Welsh Government, and will enable faster, more frequent services between Cardiff and the heads of the valleys.
