The M6 and M4, which form the Galway–Dublin route, consist of a grade-separated 2+2 dual carriageway road with a top speed limit of 120 km/h.

This section lies between the town of Ballinasloe and Galway City, running between junctions 14 and 20 on the M6 corridor.

[3] The PPP contract was awarded to N6 Concession Limited in April 2007 which comprised FCC Construction S.A. and Itinere Infraestructuras (both major companies from Spain) and P.J.

The environmental agency An Taisce claimed that the National Roads Authority's planned route would be "particularly destructive" in passing the site of the 17th-century Battle of Aughrim.

The new section of N6/M6 between Ballinasloe and Galway was also quite unusual in another way: Unlike most national road upgrade projects in Ireland, the new route differed significantly from that of the original N6.

As an emergency measure to restore access from Dublin to Galway after severe flooding at Craughwell on Friday 20 November 2009, an incomplete section of this scheme between Loughrea and Galway Clinic (Doughiska) was opened temporarily.

R446 ‒ Milltownpass R389 – Kilbeggan N55 ‒ Cavan, Longford, Athlone R355 – Portumna R347 ‒ Craughwell M18 ‒ Limerick At-grade roundabout junction.

It opened in February 2016 and its facilities include a Supermac's, Papa John's Pizza and Spar.

Subject to improvements, the Athlone Bypass may yet come under motorway regulations and be incorporated into the rest of the M6 route.