The A6 road in Northern Ireland runs from the Belfast to Derry, via Antrim. Mostly single carriageway, there is a short dual carriageway section forming the Toome bypass. Towards Derry, there is also a short section of dual carriageway at Altnagelvin. This is one of Northern Ireland's most important arterial routes, as the road runs between its two largest cities and urban areas. Between Randalstown and Derry the road forms part of European route E16.
The road begins at Carlisle Circus in north Belfast, and runs through Glengormley, Templepatrick, Antrim, close to Randalstown, Toome, close to Castledawson, close to Maghera, then over the Glenshane Pass to Dungiven, finishing at the Craigavon Bridge in Derry. Between Belfast and Antrim, the M2, and between Antrim and Randalstown, the M22, run almost parallel to the A6. At Randalstown the M22 rejoins the A6.
Investment in the northwestern region has recommenced with two separate projects under development which will see 26.5 miles (42.6 km) of high-quality dual carriageway constructed. The A6 Dualling Dungiven to Derry scheme will see 18.8 miles (30.3 km) of dual carriageway constructed at an estimated cost of £320m. In addition, the A6 Dualling - Randalstown (M22) to Castledawson project will see 7.7 miles (12.4 km) of dual carriageway road constructed at an estimated cost of £100m.
The remaining 19 miles (31 km) between Castledawson and Dungiven has not been allocated funds to develop the last stage of the dualling; it is widely hoped that by the time construction is underway on the Derry-Dungiven stretch, further funds will be made available and the two largest urban centres in Northern Ireland will finally have a high standard dual carriageway link, although this looks unlikely in the current economic climate.
In June 2008, Regional Development Minister Conor Murphy announced plans for a feasibility study into creating an A6-A5 Link Road around Derry. This will more than likely also be of HQDC standard. It has been noted that this is not a commitment on behalf of his department.