Originally Posted by ACustomer
Eddie: Belfast to Coleraine is single track from about 6 miles outside Belfast. (It used to be double as far as Ballymena). What makes the present service on the Derry line so good is the absence of a very intensive and slow suburban service like the DART getting in the way of everything.
Apologies, in fact looks like there's an hourly service, Belfast to Coleraine (not every 30 minutes as I first thought) with a connecting service to Portrush which makes a single line possible.
That means you just need 30km of single track to be laid between Dublin and Greystones (with the odd passing place), cutting the investment required significantly to get the significant benefit improvements to the rest of the line.