The A5 is the main north-south road in the west of Northern Ireland connecting the A4 at Ballygawley via Omagh and Strabane to Londonderry. From an all-Ireland perspective, it forms a key part of the route from Dublin to Donegal and Derry. At the time of writing (March 2008) the entire road is single-carriageway. This scheme would see the approximately a third of the route at the northern end upgraded to 2+1 standard including a new bypass of Sion Mills and an upgrade of the existing Strabane Bypass. "2+1" means that the road would be single-carriageway with an overtaking lane that alternates between the northbound and southbound lanes every mile or two. The screenshot from Google Earth (below) shows the scope of the upgrade.

This scheme was first suggested in the DRD consultation document "Expanding the Strategic Road Improvement Programme 2015" released in July 2006. It was superseded by the announcement in July 2007 that the entire A5 was to be upgraded to dual-carriageway standard with a large percentage of the cost met by the Republic of Ireland. However nothing is certain until the bulldozers move in, so if the A5 dualling scheme fails to happen this lesser scheme may still take place.