An upgrade of the road between Belfast and Londonderry could be fast-tracked after a legal challenge left plans for another major dual carriageway across Northern Ireland in disarray.
The redevelopment of two sections of the A6 has emerged as a potential alternative to the troubled £330 million A5 project between Londonderry and Aughnacloy in Co Tyrone.
Roads minister Danny Kennedy announced he will not appeal against a High Court ruling that had quashed his original decision to proceed with two parts of the A5 - from New Buildings to north of Strabane in Co Londonderry and from south of Omagh to Ballygawley in Co Tyrone.
Mr Justice Stephens found in favour of the Alternative A5 Alliance lobby group, which had challenged Mr Kennedy by means of a judicial review.
Justice Stephens found that an appropriate Habitats Directive assessment on the potential impact on the River Foyle and River Finn Special Areas of Conservation (SAC) had not been carried out.
Mr Kennedy said he accepted the decision and would now commission a more comprehensive assessment - a process he conceded would result in a "substantial delay" to progress on the A5 project.
Mr Kennedy said he now hoped to work with Executive colleagues to ensure that money was diverted to other projects that are almost ready to go. These include the widening of the Knock dual carriageway in Belfast and a by-pass around Magherafelt. But it is understood that the A6 project is at the top of the minister's wish list. The plan incorporates the construction of two separate sections of dual carriageway - between Londonderry and Dungiven and between Castledawson and Randalstown.
The Alternative A5 Alliance welcomed Mr Kennedy's decision not to appeal. Spokeswoman for the group Laura Kwasniewska said: "All our supporters will be delighted to hear that common sense has prevailed at long last.
"They have lived with the threat posed by the new road scheme for the past four and a half years and it has taken its toll on the health of many individuals. Householders as well as business people and landowners have had good reason to dread the construction of this unnecessary road.
"Environmentalists were equally worried about the scheme's impact on the countryside and places of natural beauty. Farmers in counties Tyrone and Londonderry will be relieved as well as delighted today to know that the vesting orders are now quashed and the land that was vested last September is now theirs once more."