The route connecting Galway with Sligo and the northwest is known as the N17, memorably recorded in the title of a song by late 1980s/early 1990s Irish band The Saw Doctors. It originally started in the centre of Galway city at the intersection of Tuam Road and the N6 Inner Galway Bypass. In September 2017, it was replaced with a motorway to the east, originating in the mega interchange of the M6, M18 and M17, west of Athenry, and terminating west of the small town of Tuam.
A very poor quality section of route follows, as the road negotiates bogs, fields and hills. South of Claremorris, an old good quality grade separated single carriageway road takes the route further past Knock, apparently the scene of an apparition of the Virgin Mary in 1879. North of here, the route is very poor the whole way to Collooney. It passes Ireland West Airport Knock, also known as Knock International Airport, the N5 at Charlestown, and the town of Tobercurry (pronounced Tub 'r' curry), which sounds like a dish of Indian takeaway.
The whole route from the end of the motorway at Tuam to the far end at Collooney will eventually be replaced with dual carriageway, though no end date for this has been set.
Update 06/10/2019:
Collooney-Knock is now in route selection, with its own website.
Update 23/08/2021:
The route options for the Knock-Collooney scheme have been narrowed down as the latest map shows.
The main change from before is that routes which were far to the west or east of the existing road have been removed from consideration.
The routing proposals are particularly close to the current route of the N17 at either end of the scheme, running online (right on top of it) for the final few km.
The plan is to build this scheme as a dual carriageway.
Update 01/02/2022:
The new grade-separated junction on the N17 south of Claremorris will start construction in the next few days.
Update 30/06/2022:
The grade-separated (flyover-style) junction south of Claremorris has been under construction for a few months and is making rapid progress.
Here is a recent tweet that gives an overview of the progress of the structure so far.
The junction is expected to open in Q1 of next year.
Update 27/02/2024:
As part of the N17 Knock to Collooney upgrade, the Tobercurry and Charlestown bypass elements are to be progressed first.