Translink is set to carry out essential engineering works on the line on Sunday, May 28.
To facilitate the works, there will be a line closure between Belfast Great Victoria Street and Portadown stations, with bus substitution services in place for local rail and cross-border Enterprise services.
Enterprise services will operate as normal between Portadown and Dublin Connolly, with bus substitution in place between Belfast Lanyon Place and Newry. An express coach service will run from between Newry and Belfast Lanyon Place.
Normal rail services will operate between Belfast and Bangor. Train tickets will also be valid for use on appropriate Ulsterbus and Metro scheduled services.
Translink says there may be minor alterations to some services to accommodate bus substitutions. Passengers are advised to plan their journey in advance using the Translink website www.translink.co.uk; the Journey Planner or by phoning the contact centre on 02890 666630.