Given we have left the EU I think any cross border service improvements will happen for a while due to the uncertainty of that route.
The biggest obstacle to journey time improvements on the Dublin - Belfast line is the congestion approaching the two cities.
Transferring the route to Great Victoria St would cut 5 minutes and it is better located but improving speeds south of Malahide is going to be impossible with the frequency of local stopping services which are due to increase later this year. Short of quad-tracking from Connolly-Howth Junction there is no solution to this.
One thing I have noticed though in Northern Ireland is all services seem to be concentrated on the Belfast area I think it would be useful to do what they do with the bus branding in Northern Ireland (Ulsterbus for outside Belfast and Metro for inside Belfast) and have something like UlsterRail for the Belfast to Londonderry, Belfast to Newry and Coleraine to Portrush while inside Belfast on the trains to Portadown, Larne and Bangor use MetroRail.
That was tried before with Intercity and Suburban branding in the 90's, it wasn't really a success with the small network and inability to keep the stock on the correct services.
Currently all the stock is the same so what would be the point, Translink have progressively watered down the individuality of the 3 companies so it wouldn't really fit their current thinking anyway.
Realistically though would would be the maximum speed for a Belfast to Londonderry service? I think its 50mph at the moment which is far too slow for an inter-city route if you ask me.
What is the top speed that any Irish Gauge train ever built by the way?
NIR MU stock is 90 as is Enterprise, IE 201 locos + stock, 2200 railcars are 100 mph, the rest of their diesel railcars are 75mph, 071 locos are freight only now but are 90mph capable.
Agreed. The only competitive advantage it can have is reliability (as compared to the very variable Belfast traffic). To do so will require significant investment in double track/passing loops so that minor delays don't balloon into major disruption.
There is already a scheme due to start construction next year to improve access to Belfast from the M2 direction with the M1-Westlink-M2 becoming entirely freeflow which will provide a very quick route to Europa Bus Station.
As well there are plans for dualling a large proportion of the A6 from Derry- Dungiven and extending the M2 end as well.
By the time any rail improvements are forthcoming the road route will already be quicker and less delay prone, Belfast-Derry is one route that rail has no realistic chance of matching road journey times. Having said that the passenger numbers are healthy and growing on the Derry line so while it won't be the quickest it does seem to have a healthy future.
It really is a shame that the post war Stormont government was violently opposed to rail as if they had survived a number of the lines closed in the 50s and 60s would be very well used today. Certainly the Derry-Portadown-Belfast/Dublin route is a great loss as well as some of the County Down commuter lines.