Some rail disruption is expected as part of the £50m north Wales railway upgrade project comes into use for the first time this weekend.
Engineers will carry out final testing and commissioning of the new signalling system between Shotton in Flintshire and Colwyn Bay in Conwy county.
Replacement bus services will operate between Llandudno Junction and Chester.
Network Rail said the upgrade would increase the resilience and reliability of the railway.
Richard Evans, programme manager for Network Rail Wales and Borders, said: "We will be working closely with Arriva Trains Wales and our industry partners to minimise disruption to passengers and residents as we complete this essential work."
There will be a replacement bus service between Llandudno Junction and Chester on 24 and 25 March, 8, 15, 22 and 29 April and 13 May.
Bethan Jelfs, Customer Services Director for Arriva Trains Wales urged passengers to check before they travel.
As well as the new signalling system, the north Wales railway upgrade project includes the installation of new track along the line in Flint, Rhyl, Mostyn and Abergele.
The project is set to be completed by the summer.