The A3 is the principal route from Lisburn to Monaghan, but one of the most trafficked portions is the 14km stretch from Portadown to Armagh. This is the main route in and out of Armagh from the Belfast direction. In 2006, the Armagh Road in Portadown carried 17,136 vehicles per day, close to the 18,000 threshold where a dual-carriageway is considered necessary. The route consists of a fairly flat and fast stretch from Portadown to the Stonebridge roundabout at Richhill and then a much twistier section from there to Armagh. The route features an overtaking lane at the Armagh end but tends to get congested at other points.

The proposal is to dual the stretch from Portadown as far as Richhill. The stretch from the roundabout at Armagh Road, Portadown to the Stonebridge roundabout is 5.5km, so the scheme will either include the dualling of 1km beyond Stonebridge, or else part of the road system within Portadown. The road will be constructed as a "standard" dual-carriageway with central reserve crossing points (as opposed to "high quality" which features grade separated junctions).

This scheme was first proposed in the document "Expanding the Strategic Road Improvement Programme" released for consultation in July 2006. This document envisaged an extra £400m for roads in the period to 2015. This scheme was one of two which attracted the media's attention (along with the A1-M1 flyover at Sprucefield) as it was seen as a somewhat unexplained choice given the number of routes that would benefit from such an upgrade. Also, if traffic figures are to be believed traffic is actually heavier on the Richhill to Armagh section than on this section (20,952 vehicles per day on the Portadown Road, Armagh in 2005).