<P> Passenger railways are operated by Northern Ireland Railways . With Iarnród Éireann (Irish Rail), Northern Ireland Railways co-operates in providing the joint Enterprise service between Dublin Connolly and Belfast Central . The whole of Ireland has a mainline railway network with a gauge of 5 ft 3 in (1,600 mm), which is unique in Europe and has resulted in distinct rolling stock designs . The only preserved line of this gauge is the Downpatrick and County Down Railway . Main railway lines linking to and from Belfast Great Victoria Street railway station and Belfast Central are: </P> <Ul> <Li> The Derry Line and the Portrush Branch . </Li> <Li> The Larne Line </Li> <Li> The Bangor Line </Li> <Li> The Portadown Line </Li> </Ul> <Li> The Derry Line and the Portrush Branch . </Li> <Li> The Larne Line </Li>

What's the difference between republic of ireland and northern ireland