Named the Outer Ring Road, the route, which is dual carriageway, runs from the N4 at Lucan to the N81 at Tallaght, bypassing west of Clondalkin (around Grange Castle) and crossing the N7 near Citywest.

This facilitated works on the line, which began in February 2009,[1] to proceed without having to make any further alterations to the road.

Although provision had been made for the route to head further northwards, crossing the Liffey and joining the R121 road at Porterstown, the future bridge[2] to be built linking these points will be for the proposed Metro West only.

[3] It was eventually completed with the semi-rural section through Grange Castle built as standard dual carriageway; two traffic lanes plus hard shoulder in each direction.

It remained unopened for a time as Dublin City Council insisted that the bus lane run outside the hard shoulder so as to leave only one traffic lane (effectively the bus-lane would run down the centre of either carriageway).