The N6 is the main route from Dublin to Galway. Since 2009 almost all of it has been upgraded to motorway standard and therefore classified as the M6. Just two short sections – from Junction 8 to Junction 13 (the Athlone bypass) and from Junction at Oranmore 19 to the terminus of the route at Junction 20 – remain non-motorway and have a combined length of 18.8 km.
The Athlone bypass is an all-purpose road, allowing non-motorway traffic between the N55, N61, and N62 to avoid the town centre.
The second non-motorway section runs west of Junction 19, where the M6 ends, to the terminus of the route on the west side of Galway city. Junction 20, the Coolagh Roundabout, is at-grade with the N67, after which the N6 becomes an urban dual carriageway running around the north of the city, reducing to a single carriageway after meeting the R865. After crossing the Quincentenary Bridge, It ends at a junction with the N59, which provides access to the west coast of counties Galway and Mayo.
A section of the HQDC N6 west of Kinnegad that has since been upgraded to motorway
The N6 originally started on what was the N4 in the centre of Kinnegad, and ran west along Althone Road. It was rerouted onto a single carriageway bypass in the 1980s, which has since been replaced by motorway. Most of the old road from here to Galway is now the R446, then the R338 to the junction with Tuam Road, then the R336 through Galway city centre, meeting the then N59 at the western end of the Wolfe Tone Bridge.
Roads Act 2007 (Declaration of Motorways) Order 2009 - This instrument converts the following sections of the N6 to motorway: Athlone to Ballinasloe (also known as the N6 Ballinasloe to Athlone Dual Carriageway Scheme), Galway to Ballinasloe (also known as the N6 Galway to East Ballinasloe Dual Carriageway)