Work is "almost complete" on a new £133m dual carriageway - but transport officials have been unable to say when it will fully open to the public.
Construction has been ongoing on the A8 for three years but issues with the new Belfast to Larne road were discovered during the summer.
As a result, temporary lane restrictions, including a 40mph speed limit, have been in place along parts of the busy freight route.
Problems with sections of the road were identified when TransportNI and the contractor, Lagan Ferrovial Costain Joint Venture, carried out joint testing.
According to the Department for Regional Development (DRD), "some of the material within the surface layer was substandard".
Following further checks, unsuitable material was identified "in a number of additional areas".
The contractor starting replacing the surface - at no cost to the department - earlier this month.
The major project has brought the whole Belfast-Larne road up to dual carriageway standard and was initially due for completion at the end of May.
Asked when the remedial work will be complete, the department did not give an exact date.
A spokesman for TransportNI said work is "almost complete and the majority of the road has been opened to traffic".
"At the end of June the contractor replaced substandard surface layer material along part of the route, at their own cost," he said.
"Following the results of further inspections and testing, the presence of unsuitable material was identified in a number of additional areas of the surface layer.
"TransportNI, in conjunction with the contractor, has taken immediate action to address the issue and the contractor will be replacing the affected surfacing to ensure that they meet the standards we require. There will be no cost to the department."
Roads expert Wesley Johnston said the DRD typically carries out tests at the end of any major road scheme.
"In this case, it was found that some of the tarmac that had been laid was not as per the specification," he said.
"As a result of this, the contractor has been replacing the affected material at their own expense, and this has required lane closures and temporary speed limits during September.
"The episode serves to illustrate the value of these checks - if they had not been carried out the taxpayer could have ended up footing the bill for repairs at a later date."
